Some better sources. (Score 5, Informative)

Hi, I would avoid trying to deal with Golden Island Motor directly for ordering a single conversion kit, they don't do the english/communicating thing very well and the cost to wire transfer and ship just one hub motor will exceed the listed kit price considerably. You can get very similar value hub motors that are distributed locally through http://www.wildernessenergy.com/ and http://www.evsolutions.net/, a supplier of the http://www.crystalyte.com/. These are all direct drive motors, no gears to wear out and perfectly silent, but also fairly heavy for their power output.

I've also ordered reasonably cheap hub motors from http://www.elebike.com.tw/. They have an interesting selection including some internally geared models, and are quick to respond to queries.

Good Batteries continue to be the biggest hurdle for DIY e-bike experimenters because even though there are tons of asian companies that reportedly make them for cheap, there are simply no local suppliers. If you don't mind trying to import from China, some companies to check out:
1 http://www.peacebay.com/,
2 http://http//www.hyperbattery.com,
3 http://splendidbattery.com/,
4 http://www.gmbattery.com/,
5 http://www.thunder-sky.com/en/index.htm

Personally haven't ordered from 1 or 2 yet, 3 has very reasonably priced lithium polymer ($.82/watt-hour) and NiMH ($.40/w-hr) packs and will sell in individual qunatities. My favorite so far are the prismatic NiMH packs from 4, GMBattery, because you can access each individual cell and restack them easily. Finally there is the infamous thundersky who have lithium-ion batteries for less than most companies' NiMH. Their old 10Ah 36V setup had no protection circuitry and a few problems, but their new 20Ah 36V ebike pack looks a bit more reputable. Note that the 24V 4Ah NiMH packs from batteryspace.com that someone recomended are GARBAGE. Ours turned out to have only 2.6 Ah capacity and couldn't deliver more than about 5 amps. If you buy from batteryspace, be sure to get the 30Amp high rate pack.

Lead acid isn't really that bad if you're generally doing ~20km ish trips so you can get away with lower capacity pack. NiMH has about twice the energy density, and Lithium packs are 2-3 times better than NiMH.

I see a lot of people here have misconceptions about ebikes and exercise. I find I pedal as hard or harder riding an assisted bicycle than a regular bike. The difference is that I move at 42km/hr instead of 26, I don't slow down on the hills, and no matter how hard I work I don't get sweaty because the breeze at those speeds is so strong. This is a much overlooked fact of ebiking, the wind keeps you cool and dry.

Justin Lemire-Elmore