i built my first pc which i am still using with asus a7a266-e with amd1800.
never had any problem with it and was told that is very good combination for pc amd+asus.
Bear in mind that athlons need good cooling (thought after you buy motherboard)
in fact there are a lot of good mobo's, it all depends on what you want. If you want good overclocking capabilities, today, I would go with an Abit Nforce mobo. On the other side Epox and Gigabyte make good mobo's too. Epox mobo's can increase the voltages a lot, even so much that the condensators blow... or you mobo mosfets get fire. Still some people only want Epox. Asus is a 'stable' choice, it's a well known brand with good mobo releases.
Some cheaper mobo's like MSI, DFI, Elitegroup are good candidates for a box, it all depends what you want. speed, stability, OC, price, upgradability, ...
Go with ASUS! For reasons I stated earlier, you cant lose!