Good thread,
To add .... I flit between a strida3 and a Brompton L3 for a commute to and thro London, and frankly the simplicity of the strida's single speed, takes some beating, the only time I want the Brommies higher gear is down long v gentle slopes (eg Hyde Park) where, unless I put the cadence well into the red zone, the strida gets overtaken. Otherwise in all other give & take city riding I find single speed is best.

I saw a singlespeed folder on Wednesday. It's pretty awesome, you can buy them in Boston at Ferris Wheels kitted out a little racier than your typical folder. http://www.neobicycle.com/foldingbike/foldingbike.html

I wish I could remember the manufacturer's name, but it's a stock model with a different build kit.

Instead of hinging, the top tube telescopes. It's pretty cool.

Speaking of Neobike, http://www.neobike.com/ -- Availability will be difficult in the US though.

Oh, you could also just get an old folding Raleigh 20 and fix it. Sheldon has one of these.

anyone fix a dahon? I've seen many raleigh 20's and a few swifts fixed on fgg, but no dahons.