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.
The ASUS P55TP4XE motherboard appears to be a good choice for mid-to-high range Pentium server and workstation systems. If you're really looking for performance, be also sure to get the pipelined burst cache module . I feel that it's worth the extra cost. If you're looking for a 486 class motherboard, you might also investigate ASUS's 486SP3G offering.
NOTE: The Intel Triton chipset based motherboards do not offer memory parity logic, making it almost impossible to detect when a memory error has occurred. Those wishing to build highly fault-tolerant systems may therefore want to wait for Intel's newest generation of motherboards based on the Orion chipset or investigate ASUS's SiS chipset based motherboard, the P55SP4 . I have no personal experience with this motherboard, but have heard good things about it and will note that it has the advantage of being available now.
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 2940 for PCI. I've currently heard nothing about Buslogic's new Bt-930 controller but would welcome any reports on its performance.
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 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.
I do not currently see SCSI WIDE drives as a necessary expense unless you're putting together an NFS or NEWS server that will be doing a lot of multiuser disk I/O.
If you can also afford to buy a commercial X server for $99 from X Inside then I can heartily recommend the Matrox Millenium card. If free X servers are more to your liking, you certainly can't go wrong with one of Number 9's cards. Their S3 Vision 868 and 968 based cards (the 9FX series) are no slouches either, and are supported by XFree86 's S3 server.
I have had very good luck with the Sony Multiscan 17SE 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. $2,500 for a 21" 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, none are both cheap and good!
I can recommend the SMC Ultra 16 controller for any ISA application and the SMC EtherPower or Compex ENET32 cards for any serious PCI based networking. Both of the PCI cards are based around DEC's DC21041 ethernet controller chip and other cards using it, such as the Zynx ZX342 or DEC DE435, will generally work as well.
If you're looking for high-speed serial networking solutions, then Digi International makes the SYNC 570i series, with drivers now in FreeBSD-current. Emerging Technologies also manufactures a board with T1/E1 capabilities, using software they provide.
I currently use the Gravis Ultrasound MAX due to its high sound quality and full-duplex audio capabilities (dual DMA channels). Support for Windows NT and OS/2 is fairly anemic, however, so I'm not sure that I can recommend it as an all-around card for a machine that will be running both FreeBSD and NT or OS/2. In such a scenario, I might recommend the Creative Labs AWE32 instead.