Having trouble sending a large attachment through your company's size-stingy mail server? Try switching over to your Gmail account. The maximum Gmail attachment size is now an impressive 25MB.
Of course, that's only half the equation: The recipient's mail server must support attachments of that size as well (not a problem if he's a Gmail user, natch).
If your beefy attachment bounces, or you need to share a file larger than 25MB, your best bet is a service like Drop.io or YouSendIt, both of which support files as large as 100MB. After you upload your file, the recipient receives an e-mail containing a download link.
Of course, for really big items, you'll need a service like File Dropper, which accommodates files as large as 5GB.
Getting back to Gmail, if you have trouble attaching files larger than 10MB, bop into Settings, General, then switch to Basic attachment features in the Attachments section. That should do the trick.