You won't find anything better than 7-Zip/WinRaR/WinZip for general purpose compression, and it won't help much (about 1%) on jpegs. You also won't find much better than jpeg for photo type images or png for logos/cartoony graphics. Many people have worked on compression algorithms and they are only going to make small improvements from now on, in the general case, rather than any huge breakthroughs. Even if you came across some advanced technique like fractal compression, the receipients wouldn't be able to decompress it.
You need to decide what picture quality and size is important. If you reduce the images to jpeg 20% quality and 800x600 size, it will make an enormous difference compared to jpeg 100% and 12 megapixel say. If you really need the best image quality and full size, then post a DVD to the receipient, use an upload site or otherwise share a folder.
There is also the question of whether the receipients need the full size image immediately. Maybe you could send thumbnails which link to larger images on a web site? That way they only get what they want.