Firefox is the browser of choice of many technically savvy individuals. Over half of the people that visit STUG's website already user Firefox! If you are not using Firefox, it is worth checking out. Firefox 3 adds features that really set it apart from every other browser on the market.
BullZip is a very simple PDF printer. If you already have Adobe CS3 then this probably isn't necessary. For everyone else, this small application installs a printer that can turn any document that can be printed into a PDF file. This is an excellent format for submitting documents to other people who may not be able to open them.
ALZip is a very robust program. It allows almost any compressed file including ZIP and RAR files. It can also compress files into many different including common and not-so-common formats. This is a must have tool for anyone who will need to open compressed files. Having this installed will save frustration when you stumble across an obscure file format.
VLC media player is considered one of the best ways to view videos on a computer. This very small, almost minimalistic player can play anything that is thrown at it. It is famous for being able to play DVD players without having to purchase expensive DVD playing software. VLC is also a great way to watch those downloaded episodes of Tablet Tips.
PDF Annotator is not a free product but allows for the writing and annotating of PDF files. The alternative is printing to Journal and then to PDF, which tends to degrade the quality dramatically.
Autodesk SketchBook Pro is not a cheap piece of software. For those serious artists out there looking for a very robust tool this is a must have. For everyone else, it would be best to look for something free. If all else fails, you can always use Paint with your tablet.
InkSeine is a research product from Microsoft that is showing a lot of potential. While it appears to compete directly with OneNote, it uses an interface designed specifically for pen input. While it might not be an application that is used every day, it is undoubtedly fun to play with.
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Opera
I think Opera should be worth mentioning. I enjoy it better than Firefox.
Opera
Funny you say that, I'm currently using Opera. I definitely think it is a piece of software worth mentioning. I always end up using it whenever Firefox decides to go crazy, which it seems to do far more often than I would like. Firefox 3 is really nice, but Opera is definitely still smaller and faster, although some website still don't work correctly.