Pathfinder - It's like a simpler and more enjoyable version of 3.5 D&D.
3.5 WotC - The standard character sheet from the 3.5 Player's Guide (Wizards of the Coast).
3.0 WotC - This is the same as what is in the back of the 3rd Edition Player's Guide.
Bastion Press - A nice alternative. Easy to find out what is where on your person.
Nifty One - Calculates everything for you. This one is awesome if you have the full version of Adobe Acrobat so you can save your changes and load it up again later. Appears to be based on the one from Wizards of the Coast.
Psionics - The one from the back of the Psionics Handbook. There is also other sheets based off this one: Psychic Warrior.
If this isn't enough for you, you can check out these sites for more character sheets:
- Pathfinder - More sheets from Paizo Publishing
- Dungeons and Dragons Adventures