I use acdsee, but I wasnt aware that you could edit images (other than convert to different format), am I using an outdated version?
PhotoShop if you have money, use GIMP if you don't. PICASA from Google is also handy for quick fixes.
Photoshop usually, but I coded a php script that does that for me. Simply upload select size and the rest is left to the imagination . Imageshack is cool too.