d00d, Irfanview.
www.irfanview.de
It's such a fantastic program. It opens damn near anything and saves to damn near anything, with options out the wazoo. It still remains classy though, and is lightweight. It also opens text and some video/audio!!!
It really isn't a manipulator though. You can crop some stuff and do a ton of resize/resample sorts of things, and while there are tons of options I have never dug into, it's safe to say it is no photoshop, PSP, or even mspaint.