I usually go to TigerDirect. They're good with
information about the products. It can be very
confusing sometimes, though. A few years back
I needed drivers for a Via chipset. I think the board
may have been MSI. The board maker claimed
they had very limited support, but at the Via
website they had one download that supported
all Windows versions.

I've been using Asus for my last few boxes. I
don't really have a reason for that. It's just that
I used one once and it was good, so I stuck with
them.