I use the ones pictured below on my Droid and iPod touch. They go on with no bubbles and they do not affect screen sensitivity at all. They do tend to accumulate finger prints, though, which is the only negative thing about them. They have a smooth texture just like the screen itself. Can be had on ebay in packs of 3 for about $1.00.
http://cgi.ebay.com/3-LCD-Screen-Pr...wItemQQptZPDA_Accessories?hash=item3efce301f0

http://cgi.ebay.com/3-LCD-Screen-Pr...wItemQQptZPDA_Accessories?hash=item3efce301f0