We're all faced with the problem of e-mailing large files. This task can be made simple by using Mac OS X's built-in "Compress" tool. This feature makes it easy to not only compress one file into a ZIP archive, but also multiple files or entire folders. Just select the files you need to ZIP and right-click on one of them. When you select Compress, then in a couple seconds (this will take longer depending on the file size) you will be presented with a nice ZIP archive containing all of your files in it. Just drag the ZIP file into your e-mail and send!
There are alternatives, such as StuffIt
Expander Deluxe, but if all you are doing is compressing files, there really is no need to spend money since Mac OS X will zip and un-zip the archive handily.