I hate lists of links you easily get lost in. Here, I try to provide commented links. It still is my opinion on the contents but it may help you to estimate the chance of finding what you're looking for. The list isn't complete and won't get it in the future. Feel free to point me to interesting pages. This list is open to changes as my view and knowledge about other sites varies too.
I'm member of two mountaineering associations in Austria. The Österreichischer Touristenklub and the Österreichischer Alpenverein. Both provide a wide range of outdoor activity, guided tours (hiking, climbing, skiing ...). You may even rent equipment for your time out in the wild.
I'm not really organized in biking. The only thing I do regularly is a technical driving training once a year. There are 3 training centers run by the ÖAMTC, one of the two Austrian automobile associations. For nice add-ons, especially for offroad trips visit Touratech.
I'm a confessing mapaholic. There's a wide range of both conventional maps as well as digital maps on the market. Most of the digital maps are accurate enough to help you hitting the right planet. There's a significant difference between the "civilized western world" and the still pretty white spots in our digital geography. There's a golden rule for vector maps: map detail grows with "civilization". If you really want to know where you are, a 1:50000 scale paper map (or a good scan) is the minimum.
For Austria and parts of Germany maps in 1:50000, 1:200000 and 1:500000 are available on CD-ROM at the Bundesamt für Eich- und Vermessungswesen.
Navtech® has a good set of vector maps for at least the EC countries. They are accurate enough for route planning and finding your way along roads. At least you get close enough to find somebody who knows the right way. I use the Garmin® MapSource software (Navtech data) together with my GPS receiver.
Visit Därr, Freytag & Berndt or Touratech for a wide range on scanned or paper maps of nearly all regions of the world. Find good maps of France at the Institut Géographique National or Michelin.
For a top view of most "civilized" places visit Microsoft's satellite image server.
The list of dive sites I've been to (or want to visit in the future) is continuously growing. I moved it to a page of its own. There's an excerpt in German (local dive sites only!)
General links on scuba diving:
You have to show style, at least sometimes. To be well dressed in every situation I had the idea of very special bow ties (a white leather one for biking and a yellow neoprene rubber one for diving, up to now). Martin Mascherl ist the place to go. They'll even do individual ones on request.