I don't know about you guys, but I had loads of the stuff when I was younger. I rediscovered my collection a while ago while in the loft, and started to build As an engineer, I have a constant compulsion to build something, and lego lets you do that, time and time again. I particularly liked/like the 'Technic' range, which includes motors, gears, axles and pneumatic components, so lets you build models that actually work. I enjoy the challenge of building a working, roughly to-scale model within the limits of the available parts.
I don't tend to take many pictures of what I build, but here's one of a 4x4 truck I built a while ago. It is driven by two motors and steered by another and works well, but needs better tyres for off-roading.
Any other Lego builders here?