Here is a good start for you, but it by no means comprehensive! It is only one Mac users' perspective (mine).
Check versiontracker.com or macupdate.com (my favorite) and download to your hearts content. I've listed some stuff I found on my computer I think you may like. You will find most of these at the above two sites, but for the rest Google them and you'll find them no problem.
Stuff in my System Preferences I consider essential:
APE Manager
ASM
MouseZoom
SkipVerify
WindowShadeX
Stuff in my Utilities folder you should look into:
Application Enhancer 1.4.6
BootCD 0.6.3
Carbon Copy Cloner
CloneX
CLIX
CINEBENCH 2003
Cocktail
Data Rescue X
DVDBackup1 Folder
File Buddy 8
iBackup
Monolingual
OnyX
Pacifist-package extractor
Preferential Treatment
Quicksilver
RapidWeaver
Renicer
Safari Bookmark Exporter
SafariSpeed
SiteSucker
Speed Freak
SuperDuper
TinkerTool
Trash It!
Trash X
URL Manager Pro 3.1.1
yade X us 0.99b Folder
Killer apps:
Office 2004 (hey, it works good for me, but I still do word processing on the OLD WordPerfect 3.5e)
Logic or Digital Performer
Firefox (download extensions to speed it up)
GraphicsConverter (not meant as a Photoshop sub, but a supplement)
VLC or MPlayer to watch movies QuickTime won't play (there aren't many that fit that bill)
DivX (not really an app, but a codex)
Toast (for more powerful burning capabilities)
PDF Shrink (for shrinking huge PDF files for web distribution)
RadioLover (record any internet radio--but it's not free)
MP3 Trimmer
TextWrangler
Sound Studio (for basic audio editing)
WireTapPro (record any sound on computer as an .aiff (.mp3 as well?))
MacTheRipper
Popcorn
Batch (for photos)
NoiseNinja (for photos)
Newsreaders: Unison, Hogwasher, Thoth, etc.
Lastly, here is good set of links for "mac os x power tools," for the real tinkerer:
http://homepage.mac.com/frakes/MOSXPT/content/software.html