Here are some of the key tutorials which I have found very helpful while exploring XNA game development:

XNA Game Studio tutorials

 Beginner's Guide to 2D Games - walks you through building a basic game with a cannon that shoots down UFOs.

 Game State Management - a straightforward tutorial that includes some nice Screen Manager classes which can be reused to help you easily add a menu to your game.

 Tile Engine tutorial - The man, the legend, the Nick Gravelyn tile engine tutorials!  A complete set of video tutorials on creating a tile engine so your players can roam across multiple screens worth of game world.

 Pixel Shaders - Learn what pixel shaders are, and how to start creating your own custom shaders.  Video session from the very promising XNA Developer Talk series. 

Inkscape tutorials

A quick guide to Inkscape - A nice brief rundown of the core functionality of Inkscape.

 Basic tutorial for novices - very basic, but decent for a visual intro.

Audacity tutorials

1.2 tutorials - some tutorials from the official v1.2 Audacity manual

Have any tutorials to recommend?  Feel free to contact me or leave a comment!