Not really a faq, I'm sorry, there's not much to say.
The BX chipset supports AGP 1.0, transfer rate 2x, 3.3V signaling voltage.
Newer cards support AGP 2.0 ("4x"), 1.5V signaling voltage, and even newer cards support AGP 3.0 ("8x"), 0.8V signaling voltage. However, almost all cards available (in June 2003) retain backwards compatibility to AGP 1.0 (they are "keyed" for 3.3V operation). This includes ATI Radeon 7x00/8500/9000/9100/9200/9500/9700/9800 cards (Built by ATI as well as Powered by ATI), all Nvidia GeForce1-4 cards, GeForce FX 5200/5600/5800/5900 cards, Matrox Gxx0 and Parhelia cards. Of course, cards from other manufacturers as well as older cards work too.
However, some very new (in June 2003) cards are no longer backwards compatible. Currently these cards are the ATI Radeon 9600 and Matrox P650/750. Expect this list to grow rapidly - likely cards released after June 2003 won't work with AGP 1.0 and thus can't be used with motherboards based on a bx chipset (they won't even fit physically).
You can't use professional graphic cards which require a AGP pro slot neither.
However, even if a card is supposed to be compatible there could be trouble. Reported cases of incompatibilites were radeon 9000 (only non-pro) with asus p2b boards. This was likely a graphic card bios issue (since the 9000pro ran fine), it's unknown if it has been resolved.
You could also get trouble if you're overclocking the bx chipset to 133Mhz FSB, as in this case you will use 89Mhz AGP clock. Cards based on Nvidia GF2-4 chips typically handle that well, as do older (7000-8500 and 9100) Radeon cards. No idea if GFFX cards still work well at 89Mhz AGP clock, but the newer Radeon (9500/9700/9800) cards are very likely to *not* work at that AGP clock (at least the early revisions 9500/9700 - don't know anything about the later revisions which fix some compatibility problems with AGP8x). No idea about Radeon 9200, and your mileage may vary with Radeon 9000 (reports indicate they don't like 89Mhz AGP clock, but I've personally tested a 9000pro in a P2B and it ran just fine - your mileage may vary). If you happen to have a card which boots up fine but will lock up in 3d mode, you can try disabling Sideband Adressing (SBA) and/or use only AGP 1x (for instance with powerstrip). It's still possible that your card just doesn't work even if it's one listed above which typically works, don't blame me for that - such is the nature of overclocking.