Pretty much always Gigabyte for me. Although some of the newer boards seem to be dropping the better features (TI Firewire chipsets are the one that spring to mind).
That, and I don't like red, so it crosses the ASUS ROG stuff off my list
Yeah. For RAM, you can get some cheap 1333 CL9 stuff for like $40. CM also makes some great cases for $60 (HAF 912). I think the M/B is the second worst place to cheap out on (PSU is the absolute worst). CPUs are fine to cheap out on, but only if you have a good upgrade path (ie. i3 2100 -> i7 2600K). A bad motherboard prevents you from going SLI/CF, overclocking, or adding more than a couple hard drives (my Biostar A880GU3 has 4 SATA ports and 2 DIMM slots).