I do a lot of screenshots for online use and for html help files. Using PrintScrn works well for this. I use Corel's Photo-Paint9 to save as either .gif or .jpg files depending on which looks best.
Everything goes well when I crop and save the graphics at 100%. But resampling is a disaster. I can't seem to find a combination that will give me good sharp output at, say, 50% reduction.
I've tried creating the file at 300 dpi Resolution and at 96 dpi then reducing but any reductions I do result in very fuzzy output.
Heres is a good primer that has several recomendations and tips for this exact situation. Just finished reading it myself, moments before I came over here and found several new tricks - Tim C.