The Tech-Recipes tips blog points out a handy shortcut that some users of the super-handy Growl Mac OS X notification tool might not know. Rather than closing every individual notification that piles up while you're away from your desktop (assuming you've configured Growl to leave notifications on the desktop), you can simply option-click on any individual "close" (x) icon to wipe them all away. Good for quickly getting back to work after a quick browse of your Growl notices. Growl: Close Multiple Notifications with One Click

Webapp Pingie takes any RSS feed and alerts you of new items in that feed via SMS message. It would be a bit ridiculous to subscribe to the full Lifehacker feed (or other frequently updating sites) with Pingie, because no one really wants 20-plus text messages a day. However, for lower volume sites, services like Pingie or previously mentioned Web-alerts could come in very handy. Pingie is free to use, requires an email address to set up your account.
Pingie

Linux only: Linux users already have a powerful Gmail notification tool in Checkgmail, but the advanced functionality doesn't always fit the bill, or even just work, for some users (including yours truly). For those seeking a more streamlined notification window, or perhaps just the same kind of tool for non-Gmail POP or IMAP accounts, cGmail is a handy taskbar tool. Once you've installed and configured your account, it's just one click to have cGmail load on startup, and the app integrates nicely with the GNOME desktop's keyring manager. cGmail is a free download, available in .deb, .rpm and source downloads for Linux systems only.

cGmail