So glad you are having this discussion - same thing happened to me today and I'm banging my head trying to get my apps back. It wouldn't matter to me if I had a backup of my 300 item to do list from Listomania - my entire life is in there - and I have no other backup.
So far I've found an old backup from last Wednesday and restored my iPhone from that backup. I know it succeeded in some way because it changed the background photo to what it was last Wednesday. My apps are still not there however. I tried what vburger did - went to applications in iTunes and synched them. I have no option to update them and in fact there are no apps in my Selected applications list in iTunes (I can't even select Selected Applications - only All Applications). Where did they go?
You had a hard drive crash and you maintain a backup for your computer's data that includes your iTunes library - the iTunes named folder where the Mobile Applications folder is located, and you restored your iTunes folder from your computer's backup?