I like paint.Net myself. Its free and if you load the plugins available you can get a lot done quickly and easily.
Best tip is to make sure you save stuff in layers so that if you only need to edit part of an image you can.
Another tip is after you finish your edits you can expand the canvas on all sides by 1 pixel then use solid black for doing the .9 marks. Once done you can dump your files right into the latest eclipse and draw9 isn't even needed which saves a lot of time.
Also 7-zip is just amazing. You can use the file manager to move files between zip files and apk and even jar files without unpacking or packing over and over.
Unlocked and Rooted Sensation 4G
Special thanks to Cyanogen, Enom, Sir*Mez, Drizzy, Manup, Jairomeo, Armyranger251, Dude, Haykuro, Stericson, JF, Lucid, Baadnewz and all the devs and themers here.