Both Abit and Gigabyte make good boards.
If you need integrated video or an mATX board then go for the gigabyte.
If you are going to use a dedicated graphics card I would recommend the Abit, a lot of the nForce 430+Geforce 6100 motherboards I have seen only have 4x-8x on the 16x PCI-e slot. I don't know if the Gigabyte one does or not.