for the mac brats, download this app/program
[Only Registered Users Can See LinksClick Here To Register] which is pretty much a no brainer. automatically makes contact sheet and saves to your desktop.
when you post your message in one of the forums, look for the "additional options" section (just below where you are typing) and click on "manage attachments" found in the "attach files" section. click browse to find your images, after selecting the image click "upload" (should then see message that files are attached) then click "submit" your message.