Online tools for instant image compression

Image Compressor - Compress your PNG/JPG files by up to 80% and retain full transparency

Advanced PNG and JPEG compressor for reducing file size without quality loss, additional tools available at the site: Image resize, Bulk resize and other PDF and image conversion tools.

Smart PNG and JPEG compression

Allows multiple file conversions (up to 20 files per job), compresses JPG, PNG and PDF's

Yet another solution, similar to