Time for a well deserved epic bump.
I've being using this site for years to optimize websites, before it was even purchased by Yahoo who I might add have done nothing to the site. Seriously wish it was Google who purchased it. End Rant!
Lately I haven't used it much as
http://gtmetrix.com (another site I love) does it but it's only useful for individual pages. Anyway today I used
http://smushit.com again. Most sites have an image folder for the theme or avatars so why not go directly to that folder and just copy and paste all the url's of the images directly into smushit. You can then download the zip folder of optimized images and just replace your existing ones with the new optimized ones. It won't take you more than 3 minutes to do your whole site but is well worth it as it will save you bandwidth and make your site load much faster.
Do it now. It's so simple and quick.