As a Windows Mobile developer with quite a few years of experience I would like to pass on a few of my favorite tools.
These are 5 programs I couldn't (or at least wouldn't want to) live without.
In no particular order:
This is an excellent freeware paint program. No it won't replace Photoshop but this is excellent for quick edits. If you can use MS Paint, you can use Paint.net. I've been using it for months and never ran into a bug.
This program is unfortunately not free. In fact, its very pricy. I'd like to tell you its overpriced but the amount of time you'll save using Visual Assist will more than make up the cost. It adds brilliant shortcuts to toggle between .h and .cpp files, it does an excellent but non-intrusive job of color coding your code. It finds spelling mistakes in comments, it has an excellent predicition engine to help cut down on typing, etc, etc etc. Just install the 30 trial - you'll love it. Note - last I checked it won't work on Visual Studio Express.
I know there are a lot of tools to do file comparisons but this one is simply flawless. Its brilliant at comparing large quantities of files and equally compitent at comparing two text files. If you need more it has a great list of free plugins for comparing images, mp3s, hex, etc.
At $30 its steal.
This program may not be essential but its a nice upgrade to Notepad with low overhead. It has color syntax schemes for most common lanuages but is still light and simple like the original notepad. I use it for doing side by side comparisions with Visual Studio. If you want just a little more functionality do a search for Crimson Editor. Both are free and both work very well.
Now this program might not be very exciting but when you need it, its perfect. I have been searching for years for a descent icon editor and have probably wasted more hours than I care to admit. I've even bought two retail icon editors but nothing comes close to IcoFX. If you're creating Windows Mobile Icons from pre-created images - this is the only program you need. It makes it dead simple to create multipage icons with different sizes and bitdepths. And it does an excellent job scaling down images. For Windows Mobile, I simply create one 64x64 image and let IcoFX do the rest.