I have SSS as well, not to mention a short attention span, so I really like doing both socks at the same time on a set of small (12") circular needles. The size needles I use just depends on the sock yarn; usually somewhere between size 2 to size 5. I use the basic sock pattern from the Knitting for Dummies book for men's socks, but there are lots of other good patterns out there. Once you get the hang of doing two socks at the same time, you may never go back!
I had a pair to do the other day and couldn't find one of the circular needles I was looking for, so I used a circular needle along with a set of 5 dpn's just so I could do both socks at the same time!