The folding bike continues to evolve, and here's one of the best, the Strida 5.0. Its folding mechanism is about as simple as you can get, collapsing in seconds into a size that fits easily into a car trunk or under your desk. It's a significant improvement over version 4, with disc brakes instead of the less-effective drum brakes. Most of it is made of cast aluminum, and instead of plastic wheels it now has alloy rims and hubs. Best of all, it's lighter than its 22-lb predecessor at just 19.4 lb. Shipping on October 25 in silver and red, early December brings even more color choices. Simplicity and feather weight have a heavy price, though, it's $799. [Strida, via Treehugger]