I know there are a lot of archivers out there and lots of related tools, but this one looks worth checking out.http://www.peazip.org/
Peazip is a free, cross platform, open source archiver that runs on Windows, Linux, and Mac. That's nice because you can use the same tool on whatever platform you happen to be on at the moment. It handles a very wide variety of formats including some new ones I hadn't even heard of. It will also split archives into chunks which is useful if you want to burn a copy of an archive that's too large to fit on one CD, DVD, etc..
I haven't played with it much yet, but I was initially impressed by it's ability to handle so many types of archives and, in some cases, to combine them. (It will let you run files through tar and then through the compression of your choice, so it will make and manipulate tarballs for those of us who use Linux.)
It also comes with an extensive manual which is often lacking in free applications.
Take a look at it and see if you like it. I'll post further once I've used it a bit more.