Considering I've been in love with my Mac for about 9 months now (And the PC just got a freeware thread, heh) , I figured I would help out all my fellow Mac users by giving you a list of great freeware apps that I use all the time.
Adium - The end all be all of IM apps. I haven't played with iChat that much, but I can tell you that this app works EXTREMELY well, it's very customizable, and incorporates with Growl.
Alarm Clock - This is a niftly little alarm clock that also acts as a timer and a stopwatch. The alarm clock will play music you have selected from your iTunes library (You can choose a specific song or have it shuffle randomly through a certain playlist). It's extremely customizable, has an easy wake and snooze option, and is compatible with your Apple Remote. You can even set the alarm clock to say, go off at the same time every day Mon-Fri, so you only have to set the clock once and you're good. The only thing I don't like about this you have to leave your computer on overnight in sleep mode for it to go off, and I like to turn my Mac off at night. The Aurora alarm clock has the ability to do this as well as many other really cool features, but that costs about $15.
AppCleaner - Sometimes just moving an app to your trash isn't enough, and this app will completely remove all parts of an application.
AppFresh - This is a really slick app that, when launched, looks through all of your apps and shows you all of the ones that have updates availible. Then you can download the updates directly from the app; no looking on google for the update! The interface is VERY well designed and overall this is something everyone should have.
Caffeine - This is a tiny little app that plops a coffee cup into your menu bar. Clicking on it adds coffee to the mug, and keeps your computer from sleeping the display. Clicking it again removes the coffee and allows your computer to go to sleep. Set it to launch at startup so it's always ready. An alternative to this is Jiggler, but since this sits in the menubar instead of being a full app that you have to launch, it's a little bit quicker to use this.
DockColor - This app will change the color of your Leopard dock to a color of your choosing. It gets the job done, but the dock just doesn't look as good as something added with LeopardDocks App (Which I'll talk about later)
Firefox or Opera - Safari is a neat browser, but it's just so darn slow among other things such as a lack of features. It's well worth it to replace Safari with FF or Opera. Both FF and Opera are great browsers and you can't go wrong with either, but right now I'm leaning towards FF because it's more compatible and after downloading some plugins it can do just about everything Opera can do and more.
iSquint - This app can quickly and easily convert most file types into the much friendlier .mp4 format.
Jing - This is a screen capture app that allows you to click and drag what part of the screen you want to take a picture of (Or just take one of the whole screen). You can then immediately annotate it with text, arrows, boxes, etc all inside the app. The best part, though, is that with a click of a button it will automatically upload the picture to the web. It can also take rudimentary video capture, which can't record sound (although it can record microphone sound) and runs at a crappy framerate, but what do you expect from a freeware app? The best way to use this is to have it start at launch and have it appear in the menubar.
Part 2 coming later.... with notetaking, text and image editing, and more.