For science Twitterers there are now lists of science Twitterers compiled:
http://bit.ly/sQWM1
(There are even lists of lists --- these are by no means all science however):
http://listatlas.com/
Personally, I won't be satisfied though until we have lists of lists of lists of lists ;-))
For science Twitterers there are now lists of science Twitterers compiled:
http://tinyurl.com/