The following list of sample hardware configurations by no means constitutes an endorsement of a given hardware vendor or product by The FreeBSD Project. This information is provided only as a public service and merely catalogs some of the experiences that various individuals have had with different hardware combinations. Your mileage may vary. Slippery when wet. Beware of dog.
I have had fairly good luck building workstation and server configurations with the following components. I can't guarantee that you will too, nor that any of the companies here will remain "best buys" forever. I will try, when I can, to keep this list up-to-date but cannot obviously guarantee that it will be at any given time.
For Pentium Pro (P6) systems, I'm quite fond of the Tyan S1668 dual-processor motherboard as well as the Intel PR440FX motherboard with on-board SCSI WIDE and 100/10MB Intel EtherExpress NIC. You can build a dandy little single or dual processor system (which is supported in FreeBSD 3.0) for very little cost now that the Pentium Pro 180/256K chips have fallen so greatly in price, but no telling how much longer this will last.
For Pentium machines, the ASUS P55T2P4 motherboard appears to be a good choice for mid-to-high range Pentium server and workstation systems.
Those wishing to build more fault-tolerant systems should also be sure to use Parity memory or, for truly 24/7 applications, ECC memory.
Note: ECC memory does involve a slight performance trade-off (which may or may not be noticeable depending on your application) but buys you significantly increased fault-tolerance to memory errors.
This one is a bit trickier, and while I used to recommend the Buslogic controllers unilaterally for everything from ISA to PCI, now I tend to lean towards the Adaptec 1542CF for ISA, Buslogic Bt747c for EISA and Adaptec 2940UW for PCI.
The NCR/Symbios cards for PCI have also worked well for me, though you need to make sure that your motherboard supports the BIOS-less model if you're using one of those (if your card has nothing which looks even vaguely like a ROM chip on it, you've probably got one which expects its BIOS to be on your motherboard).
If you should find that you need more than one SCSI controller in a PCI machine, you may wish to consider conserving your scarce PCI bus resources by buying the Adaptec 3940 card, which puts two SCSI controllers (and internal busses) in a single slot.
Note: There are two types of 3940 on the market--the older model with AIC 7880 chips on it, and the newer one with AIC 7895 chips. The newer model requires CAM support which is not yet part of FreeBSD--you have to add it, or install from one of the CAM binary snapshot release.
In this particular game of Russian roulette, I'll make few specific recommendations except to say "SCSI over IDE whenever you can afford it." Even in small desktop configurations, SCSI often makes more sense since it allows you to easily migrate drives from server to desktop as falling drive prices make it economical to do so. If you have more than one machine to administer then think of it not simply as storage, think of it as a food chain! For a serious server configuration, there's not even any argument--use SCSI equipment and good cables.
My SCSI preferences extend to SCSI CDROM drives as well, and while the Toshiba drives have always been favorites of mine (in whatever speed is hot that week), I'm still fond of my good old Plextor PX-12CS drive. It's only a 12 speed, but it's offered excellent performance and reliability.
Generally speaking, most SCSI CDROM drives I've seen have been of pretty solid construction and you probably won't go wrong with an HP or NEC SCSI CDROM drive either. SCSI CDROM prices also appear to have dropped considerably in the last few months and are now quite competitive with IDE CDROMs while remaining a technically superior solution. I now see no reason whatsoever to settle for an IDE CDROM drive if given a choice between the two.
At the time of this writing, FreeBSD supports 3 types of CDR drives (though I believe they all ultimately come from Phillips anyway): The Phillips CDD 522 (Acts like a Plasmon), the PLASMON RF4100 and the HP 6020i. I myself use the HP 6020i for burning CDROMs (in 2.2 and later releases--it does not work with earlier releases of the SCSI code) and it works very well. See /usr/share/examples/worm on your 2.2 system for example scripts used to created ISO9660 filesystem images (with RockRidge extensions) and burn them onto an HP6020i CDR.
For backup purposes, I'd have to give the higher recommendation to the Exabyte due to the more robust nature (and higher storage capacity) of 8mm tape.
If you can also afford to buy a commercial X server for US$99 from Xi Graphics, Inc. (formerly X Inside, Inc) then I can heartily recommend the Matrox Millenium II card. Note that support for this card is also excellent with the XFree86 server, which is now at version 3.3.2.
You also certainly can't go wrong with one of Number 9's cards -- their S3 Vision 868 and 968 based cards (the 9FX series) also being quite fast and very well supported by XFree86's S3 server. You can also pick up their Revolution 3D cards very cheaply these days, especially if you require a lot of video memory.
I have had very good luck with the Sony Multiscan 17seII monitors, as have I with the Viewsonic offering in the same (Trinitron) tube. For larger than 17", all I can recommend at the time of this writing is to not spend any less than U.S. $2,000 for a 21" monitor or $1,700 for a 20" monitor if that's what you really need. There are good monitors available in the >=20" range and there are also cheap monitors in the >=20" range. Unfortunately, very few are both cheap and good!
I can recommend the Intel EtherExpress Pro/100B card first and foremost, followed by the SMC Ultra 16 controller for any ISA application and the SMC EtherPower or Compex ENET32 cards for slightly cheaper PCI based networking. In general, any PCI NIC based around DEC's DC21041 Ethernet controller chip, such as the Znyx ZX342 or DEC DE435/450, will generally work quite well and can frequently be found in 2-port and 4-port version (useful for firewalls and routers), though the Pro/100MB card has the edge when it comes to providing the best performance with lower overhead.
If what you're looking for is the cheapest possible solution then almost any NE2000 clone will do a fine job for very little cost.
If you're looking for high-speed serial networking solutions, then Digi International makes the SYNC/570 series, with drivers now in FreeBSD-CURRENT. Emerging Technologies also manufactures a board with T1/E1 capabilities, using software they provide. I have no direct experience using either product, however.
multiport card options are somewhat more numerous, though it has to be said that FreeBSD's support for Cyclades's products is probably the tightest, primarily as a result of that company's commitment to making sure that we are adequately supplied with evaluation boards and technical specs. I've heard that the Cyclom-16Ye offers the best price/performance, though I've not checked the prices lately. Other multiport cards I've heard good things about are the BOCA and AST cards, and Stallion Technologies apparently offers an unofficial driver for their cards at this location.
I currently use a Creative Labs AWE32 though just about anything from Creative Labs will generally work these days. This is not to say that other types of sound cards don't also work, simply that I have little experience with them (I was a former GUS fan, but Gravis's sound card situation has been dire for some time).
For video capture, there are two good choices -- any card based on the Brooktree BT848 chip, such as the Hauppage or WinTV boards, will work very nicely with FreeBSD. Another board which works for me is the Matrox Meteor card. FreeBSD also supports the older video spigot card from Creative Labs, but those are getting somewhat difficult to find. Note that the Meteor frame grabber card will not work with motherboards based on the 440FX chipset! See the motherboard reference section for details. In such cases, it's better to go with a BT848 based board.