Fotografix is a simple free photoshop alternative in under 1mb.
In addition to being totally portable, Fotografix has a ridiculously small footprint.
Fotografix supports layers, masks, and scripting, comes with a few key blur and stylization filters, and type layers are editable.
The usual editing tools are also provided, like rectangular and elliptical marquees, magic wand, rubber stamp, eyedropper, and gradient tool.
The author's allows redistribution, i took the liberty of mirroring the app here: http://blog.libero.it/murby/10804836.html