Commonly used brushed motors,

- bosch 750w - like hens teeth to find these days but everyone used to use them
- iskra 800w - lighter than the bosch 750 and completely sealed. Still available in various voltages and configurations and can sometimes be found second hand on ebay as they are used as hydraulic motors. Expensive brand new.
- magmotors / ampflow motors - Different but essentially the same motors. Various variants available from the cheap and cheerful e series to the powerful neodymium series
- NPC T64 motors - nice all in one units from the USA that require no additional gearing and are nice and easy to attach wheels to. Downside being that they aren't cheap and need to be imported. Mind you once you take into account a gearbox they aren't all that more expensive.
- ebay cheapo scooter motors - I believe some are experimenting with these. Whether they will be of use remains to be seen

Brushless motors,

- Dozens of variants available. I believe pulsar used the 50cc ones from hobbyking to great effect. I've used scorpion motors in featherweights in the past and they have been great.

Speed controllers, brushed

- vantec - nice but expensive
- roboteq - some swear by them, others not a fan of the new versions
- wotty - Created by Ian of bigger brother fame. Need to contact him directly for pricing etc
- ragebridge - a US creation. Been used well over there. A few have made it over the pond

Speed controllers - brushless

- This be where dragons lie. Experimentation and blue smoke are the order of the day!

Batteries,

- SLA - tend not to be used nowadays. Heavy and not as much current
- nicad - not available for sale in the EU
- nimh - lower current capabilities than the lithium based tech and tend not to be used
- A123 - a lithium based chemisty with cells similar in shape to nicad / nimh. Tombstone in the US uses them along with a number of builders over there. Tend not to be used as much over here
- Life - Regarded as a safer lithium chemistry but with lower current discharge than lipo
- Lipo - the high current, give it all it's got until it sets itself on fire and then some battery tech. Although if you use high quality cells, a balancing charger and aren't an idiot about mounting them, they work just dandy.

Hopefully this is of use.