for small file sized images that I want to be able to find easily agian from a remote location i use photobucket. (like 1mb is the max i think).. other wise I use imageshack (i think 5 mb is max).. if the image is large I'll use click2host (50 mb max, if i recall correctly)
click2host is good and reliable and it does big images. photobucket is good for tags cause theyre smaller. imageshack sucks imo.
well,i use imageshack for the thumbs..then either tinypic.com/photobucket just for pics. sometimes,imageshack is slow,so it's better to use something that is not so "famous"