Have you rebooted to see if the problem goes away? Or at least logged out/logged back in?
Have you run Activity Monitor to see if there's something running you might not be aware of, or something that's hung/crashed?
Remember that an app that's running might not show in the Dock. It might be invisible, or it might show in the menu bar.
If rebooting or logging out/back in doesn't fix it: Have you checked your login items in the Accounts pane of System Preferences to see if something is launching at login that you didn't want?
If you were to run all 14 apps in the MacHeist bundle at the same time, any computer would be taxed. 3D games like World of Goo and Cro-Mag Rally can really put your processor and graphics through their paces, and BoinxTV and WireTap Studio are designed to run in the background recording your screen or your voice.
Definitely check your login items, then reboot, and see if the problem goes away. If not, use Activity Monitor to figure out what's taxing the computer so badly. You might also try creating a new user and see if the problem exists there too, or just on your main account.