that social security site
Rachel provided has some neat stuff on it. One is a listing of the top 50 most popular choices for twins. Take a look-see:
http://ssa.gov/OACT/babynames/twins.html
If you had to choose an option for g/g, b/g and b/b twins from those charts, which would you pick?
I'd go with:
Anna and
EmmaGrace and
John (or
Lily and
Luke)
James and
William
But they would have really fun middle names I swear.