GMax: This is an easy to use but relatively powerful 3D Modeling tool. It has an active community that's newbie friendly so you'll get plenty of support! There are scores of great tutorials and the forums are welcoming and remarkably patient. Best of all when used in conjunction with NWNmax the models you create and animate are completely compatible with NWN1. Give it a try. 3D modeling is easier than you think!
Pixlr: Map making utilities suck. Well... Campaign Cartographer is pretty cool, but that costs money. Don't waste your time trying to find a free mapping utility. Either scan your hand drawn maps, or get a tablet and stylus and use a good piece of graphics software. I recommend Pixlr. Pixlr is an amazing online graphic design tool that looks and feels very much like photoshop. It doesn't support channels and paths so it's not quite suitable to professional design, but it's without doubt the best freebie out there for graphic design work.
Paint.net: Paint.net isn't nearly as utilitarian as pixlr, but for freeware it's still a damn fine piece of software. It supports layers and has a huge library of downloadable plugins, but it's biggest advantage is that you don't need to be online to use it.
OpenOffice: Everything you need to write games, manage projects, and much much more. Open office is free and offers a first class word processor. It also supports spreadsheets, Database management, and much, much more. Think of it as MS office without the expense and crappy tech support.
PrimoPDF: This is a freeware PDF maker and a good alternative to Adobe Acrobat for converting your documentation to PDF format.
GeoGen: Free and Open Source heightmap generator. This program is perfect for generating terrain for maps.
HME: A freeware Heightmap Editor. Ridiculously simple to use. Truth be told I use this more than GeoGen. I do mostly low rez mapping. GeoGen is overkill for games like MC2 and HME is just plain quick and dirty.
Fractal World Generator: Donjon is a really cool site with all kinds of awesome little tools. Spend some time looking around, but the Fractal World Generator is my favorite. It's perfect for generating whole worlds in an amazing variety of map formats. The terrains are extremely realistic and important factors like hydrographic percentage and icecap size can be pre-set before the world is generated. This tool is perfect for generating sci-fi worlds for games like Traveller, even on the fly.
The Foundry: The Foundry is a mission design tool used by MMO studio Cryptic. It is currently available for Star Trek Online and will also be available for Neverwinter when it gets released.
It's crap. You're going to have to be highly skilled to be able to get it to do anything remotely interesting but it IS free, and if designing MMO quests is your idea of fun than go ahead and give it a try. You'll not only get to try your hand at it, you'll also get real feedback from actual players.
OHRRPGCE: Want to try your hand out at game design? The Official Hamster Republic Role Playing Game Creation Engine is a great place to start. It has an easy to use interface and utilizes a simple but powerful scripting language to create old school DOS era jRPGs.