A good way of getting software cheap are the MacHeist bundles - basically they promote software by giving them away at over 90% off
Have a look at the currently running MacHeist 3
These are some of my favourite programs which should be installed on every Mac:
Of course there is LOTS more that you can do with TinkerTool - disable/enable the dashboard (a memory and resource hog), disable/enable PDF display in Safari, (I prefer to download pdfs) etc
The world wide web can be an annoying place - ads blink and whistle and try everything to capture your attention. I find it extremely annoying. SafariBlock blocks 99% of ads and works fine with Safari 4 beta. You don’t realize how wonderful SafariBlock is until you disable it (very simple via the menu, and necessary for a few sites).
SnapNDrag is a simple application that makes screen capture extremely easy. Just click a button to capture and then drag the result off to another application or to the Finder. For example, to e-mail your captured screen, simply drag the result off and drop it on your e-mail application.
Perian enables QuickTime application support for additional media types (like playing many different Windows avi files)
Cyberduck is an open source SFTP (SSH Secure File Transfer) and FTP browser which basically lets you use a remote ftp server (like the webspace your ISP gives you) as if is an external harddisk - just drag&drop the files between them. Multiple connections are supported. A transfer queue keeps track of the pending file transfers and supports resuming of both downloads and uploads. A simple bookmark manager ensures manageability. Core system technologies such as the Keychain and Rendezvous are supported
Describing it as a “poor man’s PhotoShop” doesn’t do it justice - it is a remarkable program which does much more than convert between graphic formats. On the PC and Linux forums people rave about “Gimp” (an open source alternative to PhotoShop) but not on the Mac. Why? Because GraphicConverter is miles better than Gimp - and a real Mac program.
It reads over 200 graphic formats, writes over 80, has tons of editing tools, has a built-in photo browser, can make catalogs and web pages, etc …
It's also really easy. Just drag in your file, and click Start. You can also choose "TV" or "iPod" size, set your quality, or even go all-out by playing in the Advanced drawer.
Bean is Open Source, fully Cocoa, and is available free of charge! MS Word, OpenOffice, etc. try to be all things to all people. But sometimes you just want the right tool for the job. That is Bean's niche.