Since payed applications aren't yet supported in Belgium I can only find free applications on the market. These are my favorites:
This one you'll need to scan the QR codes :D. You can also scan other barcodes but I didn't find much information on the net on the ones I tried.
ASTRO File Manager
The best filemanager I found for android so far.
In fact this one ain't available as a free app anymore. Only the beta was available so you'll need to look for an .apk on the web if you really want this one for free. It's a tool to change system properties based on location, date, time, etc. The properties you can change are dataconnection, wireless, flightmode, sounds, backgrounds, etc. There are several plugins available to extend the amount of events and properties.
Quick System Info
All you need to know about the system. Display processes, specs, logs, installed applications, etc.
Can be placed on desktop (widget) and displays battery level. When selected an info screen with more details is shown.
Does exactly what you expect.
The best Geocaching tool I found so far. It lets you browse the caches nearby, show details of caches, show caches on the map, navigate to a cache (arrow), log when you found a cache, etc.
Doesn't need much explication... you can set several styles.
Shows how many satellites are connected, min/max/avg speed, min/max/avg altitude, coördinates, etc.
Great for walkers and other outdoor sports. It tracks your route on a map. Also collects information (like GPS Status) and routes can be exported.
My Maps Editor
With this tool you can edit your google maps on your mobile.
Mind Map Memo: create and edit mind maps
Pintail: get location of your cellphone by sms
SMS Backup: back up sms messages to your gmail account
Shazam: recognize music playing
Ringdroid: cut music for use as ringtone
Pricewatch Scanner: scan barcodes to find prices in the tweakers pricewatch
TVGiDS.tv: tv guide
Photoshop.com Mobile: mobile photoshop (limited)
Google Sky Map: a map of the stars
Facebook: facebook application for android
AndFTP: ftp client
A world of photo: receive and send photo's from/to all over the world
Bebbled: game like bubbles
GameBoid Lite: to play gamboy roms
Magic 8-Ball: shake to get an answer from the 8-ball
PicSay: edit pictures and add fun stuff