I just recently noticed a simple method of making certain applications start themselves up upon logging in. If an application is in the dock, you can right-click it, and put a check next to “Open at Login”. This automatically adds it to your list of startup items.
Alternatively, you can open System Preferences, the go to the Accounts tab, and click on the Login items tab. Here, you can delete startup items, as well as add new ones.
Some applications which I suggest you run upon login (which aren’t already automatically launched upon Login) are Caffeine, NetNewsWire, and Mail.app. While Login applications may be convenient in many cases, don’t have too many of them, or else it could affect the performance of your computer.