Just came across a nice way to ask your visitors/customers to follow you on your twitter account. Its not really a module so no contribution on this one, just paste the code before body tag on tpl_main_page, usually just before the end.

http://www.go2web20.net/twitterfollowbadge <----- This is the site to get your code and you can look at my site how it looks mobiles-world dot com.

Cheers!

P.S. Make sure to backup before adding this code.