Do you have a need to start an app on your Mac at a particular time, or easily get it to restart after a crash or power outage? If so, Lingon 3 may be for you. It's US $2.99 at the Mac app store.
Lingon 3 can not only start an app, but it can run a script automatically at a time you specify, or if something happens on your Mac and you want something triggered as a result. An example might be to trigger an event when an external drive is connected. Here's a video that gives an example of the app being set up.
I tried the app and used it to start up a suite of things I use after I get up in the morning. It worked as expected, and the GUI allows you to specify a particular day and time for the action to occur. You can also specify that an app keep running, so it comes back up after a crash.
Some of these things can be done by writing a script, but that's not for a Mac novice. OS X also supports login items, so if you just want things to be there when you start the Mac, you don't have to buy an app to accomplish it.
There have been some complaints about this latest version of Lingon, including some from one of our TUAW staffers, that the new version has been simplified and in the process lost some good features, including the ability to create jobs for multiple users on a single Mac. Author Peter Borg says now that he is selling this new version of the app through the Mac App Store there are some restrictions about how the app has to operate.
For many users, this won't really matter, but more sophisticated users will want more. I found that Lingon 3 worked well, but didn't take me significantly beyond what I can do with login items built into Lion, other than starting apps at a given time, and crash recovery for apps. On the other hand, if you were trying to keep, for example, a kiosk running, this app would be really helpful. If those are features you need, Lingon 3 is reasonably priced, but requires Lion. If you are interested in more features, but don't care about running the app on Lion, version 2 is still available in the Mac App Store.