You probably want to send the entire Logic project, complete with all audio and MIDI files etc. So it will probably be too big to attach to an email. First, consolidate everything needed into the project folder, and .zip it.
If you have a .Mac account or your own web site, you're all set. Just send a link to the directory where your project is located, and the recipient can download it. If you don't have a .Mac account, there are many file storage/transfer sites you can use, sometimes for free or at low cost.
Here are a couple:
http://www.yousendit.com/
http://www.sendthisfile.com/
If you are using 3rd. party instruments or effects in your project, your recipient will need them too, or you can export the audio files with the sounds intact.
