Total Finder
This is my favourite add on app! It integrates with finder and gives you the ability to use tabs, split screen and much, much more in finder! You can also launch a finder window by hitting the ⌘ key twice (or whatever you designate!) http://totalfinder.binaryage.com/
HyperDock
HyperDock gives the ability to drag any window to a screen edge to resize it to full or half screen without having to use Apple's plus and minus buttons, or manually lining things up. It also gives you a few other options that are shown in the above screen shots. http://hyperdock.bahoom.com/
Splashtop Remote
Access your Mac and all of its data through your iPad. With Splashtop Remote Desktop, you can fully access and control your computer in any way imaginable. http://www.splashtop.com/remote/availability
Using More Than 1 iPhoto Album
While clicking on the iPhoto app icon on your Dock hold down the Option key. This will bring up the above window. Here you can choose between your iPhoto libraries or even create new ones! This is great for keeping your work and home photos separate!
Cocktail & MacKeeper
An easy to use interface that enables you to get the most out of your Mac. This application provides an easy way to maintain and tweak your mac without using complicated UNIX functions. http://www.maintain.se/cocktail
If you don't want to worry about maintaining or making changes yourself you can rely on MacKeeper. This app does a range of things for you automatically and restores valuable disk space while you're at it! http://mackeeper.zeobit.com/index
Time Machine Buddy & Time Machine Editor
Time Machine Buddy is a dashboard app that keeps an eye on your Time Machine backups. If you ever have a problem with Time Machine it will let you know what happened, what went wrong and can help fix the problem. http://www.apple.com/downloads/dashboard/status/timemachinebuddy.html.
TimeMachineEditor is a piece of software for Snow Leopard and Lion that lets you change the default one-hour backup interval of Time Machine. You can change the interval or create a more sophisticated scheduling. http://timesoftware.free.fr/timemachineeditor/. You can also check out TimeMachineScheduler as another option. http://klieme.com/TimeMachineScheduler.html
I am a teacher at Pt England School with a 1-to-1 netbook classroom. You can check out what we are doing in class on our blog.