There are several online services that let you upload large files that other people can then download via a link in an email. But if you do this frequently, you may be looking for a simpler solution that doesn’t have a monthly service charge. Yellow Mug Software’s FileChute 4 is a great solution.
If you have a MobileMe account, or access to space on a Web server, you can drag and drop a file onto FileChute to upload it to your server and email a link to one or more recipients. When they click the link, it opens their Web browser and takes them to the file for downloading. You can set an expiration date for downloading the file, from one to 30 days. After that, the file is unavailable for downloading. (But you have to delete expired files manually from your server.)
FileChute costs $17.95 for Mac OS X only.