Construction Toys

LEGO & LEGO Bionicles & LEGO Technic

K'nex - (love their kits for "simple machines", and "bridges" and ...) of for infinite storage space & the $$ to fill it.
K'nex Rube Goldberg machine video

Zome - for geometry & moecules & ... they have lesson plans and books like Zome Geometry book by George Hart

and what can fit them all together? Uberstix
The best prices in July 2008 seemed to be uberstix.com and fatbrain.com. There are some neat videos on Uberstix on UTube.
1: Think Outside the box
utube 2: Danes dream on NY
utube 3: Amazing sailboat
utube 4: How to build a uberstix rocket
utube 5: landshark (scavenger set)
utube 6: uberstix v. LEGO
with K'nex

My only relationsip with any of these companies/producuts is a consumer.