You could do a Rail Fence with one color in the middle sandwiched between the other color, and alternate that arrangement, or you could make a "Framed Four Patch" from www.quilterscache.com/F/FramedFourPatchBlock.html and alternate the arrangement in that for variety (or not.)
There are a lot of blocks on the quilter's cache website that are for only two colors. Cedars of Lebanon is another.
If you want to get fancy, I recommend Storm At Sea. You should be able to find a pattern for that through Google, or in the book "More Quilts from the Quiltmaker's Gift."
Hope these ideas help!