There's one point Glenn forgot to mention: GIF files support multiple "frames," which means they can be used for simple animation. I believe this feature is exclusive to GIF since, until Netscape supported it, no one had bothered with this rather obscure part of the GIF specification. PNG was designed before Netscape supported multi-frame GIFs, and the designers didn't see the point of supporting this completely unused feature. Pity.
Adding Links in Snow Leopard's Mail
Apple Mail in Snow Leopard now has a Command-key shortcut for adding a link to an email.
If you use plain-text email, this will not be helpful at all, but if you send styled email, it's a nice shortcut for adding URLs to your email messages. Simply select the word(s) you want to make into a link, press Command-K, and enter the URL to build into the link.
Check out the perks at <http://tidbits.com/member_benefits.html>
Special thanks to Ken Land, Graham Samuel, Nav Bhullar, and Stan Hall
for their generous support!