It's be a bit of a faff, but Flickr will do a range of sizes with the bonus that they are then available on the 'net
More realistically I use JPEG Optimiser. I can make dramatically smaller filesizes for a given picture size. It allows you to choose a compression for the image with a 'live' look at what the result will be. It also has options to let you vary the compression across the image.
http://www.xat.com/jpegopt/index.html
Not a freebie, tho'
Then there's Irfanview. This says it's an image viewer, but it's got a lot of handy tricks up its sleeve - best to look at the "What is Irfanview" page on the website.
A day of all things motorhome and campervan. The show is held both in the main indoor arena and across the grounds. Catering, hot drinks and food options are available. Easy access to the site and free parking included. Win one of five pairs of day tickets