LEGO is not only fun, it's also educational. Basic LEGO is fun to build, and once you get onto Techincs and Mindstorms the interest even for adults is huge. I played with LEGO until I was about 13, then rediscovered it at 16, and again in 1999, at the age of 21. The same year, LEGO won Toy of the Century.

Some interesting links...

Oh, and outside of Everything, there is much on the Internet related to Lego.

http://www.lugnet.com - LEGO users group
http://www.brickbay.com - Auction site
http://www.brickshelf.com - Good reference for pieces and sets.
http://www.ldraw.org/ - LDraw is an excellent LEGO CAD system, with many compatible editors and tools. The output can be rendered in Pov-Ray.
news:alt.toys.lego, news:rec.toys.lego - News groups.