OK, this is totally out there in the semi-obvious open, but it's so nice to finally have it! If you'd rather send real attachments, instead of inline images, here's how.
While not in the middle of sending an email from Mail, go to the Edit » Attachments menu, and revel in the new 'Always Insert Attachments at end of Message' option.
Mac OS X Hints
http://hints.macworld.com/article.php?story=20071113193906353