This is a wonderful building toy system, dating from the late 1960's in Germany. It is made by the same company that makes the gray Nylon plugs you put into holes in concrete walls, and it displays characteristic German thoroughness in its design. Conceptually, Lego Technik is similar but came about 20 years later.
Unfortunately, FischerTechnik has evolved (like Lego) towards more specialised kits that contain fewer general-purpose parts and more special parts. Even so, the range is breathtaking, from simple elements a 4-year old can understand, to computerised models using pneumatic, hydraulic and electric elements. The electronic series from the "Hobby" range in the late 1980's is a masterpiece of clarity and should be required for any aspiring engineer.
FischerTechnik was never cheap and remains expensive even on the secondhand market. Used without too much brutality it will last forever (just like Lego), so my kids are playing with the same parts as I did. If you take such a long-term view it's well worth it.
There is a huge second-hand market on eBay in Germany, so you can easily buy a complete collection or just some starter sets.
So what can you build with it? One of my latest big works was a roller-coaster for ping-pong balls, and the kids loved it. I even made a videotape that you can watch using Windows Media Player (230kb/sec, 3MB total)
I also made a rather large overhead portal crane with a remote-controlled gripper that became quite popular.