If the receiving party is going to be USING the samples in a recording, then you don't want to use a lossy compression scheme like mp3. If they are just going to be listening to your final product, then mp3 is a good solution.
Zip compression will work on a wave file, but I'm pretty sure you're only going to see a 10-30% or so reduction in file size (can't remember the last time I did this) so you're still looking at a big file. Zip compression probably won't do much to an MP3 since the mp3 is already very compacted.
As zip said (how appropriate a name in this thread!), email accounts almost always have incoming quotas. Most free email accounts that I've had the displeasure to work with are limited to 1MB incoming. Many paid accounts will be limited to 1-2MB incoming, but the user's mailbox size is usually restricted to a few megs. In other words, don't use email. Upload the file to something like xdrive and have your friend download from there.
(note, if the receiving part is going to be using your sample in a recording, and sending a wave is simply out of the question, then using HIGH quality mp3 (256kbps or better). Also, make sure you both use the same high quality converter. I recommend SCMPX as it's the best sounding free converter I've used. Easy to find and small if you search)
Slackmaster 2000
