One of my favorite new apps is a little system tray app called caffeine (and here). It's simple, yet very practical, its purpose is to inhibit a screen saver or sleep mode, which is great while watching flash videos on sites like hulu.

Caffeine is written using GTK for the user interface, so it's very GNOME friendly, but it can be used on any Linux OS. It has a PPA for Ubuntu users (see the launchpad link) and it works great for me on Ubuntu Karmic.