Tutorial for getting a USB wifi adapter to work for a Raspberry Pi without using a powered hub from Mike Worth:
It is a commonly known problem that the Raspberry Pi cannot provide enough power for most USB wi-fi adapters. This can be solved with the use of a powered hub, however I have plans to integrate the Raspberry Pi into other devices; due to space constraints I decided that it would be better to convert a dongle to draw power separately to its data connection, also taking the opportunity to reduce the distance that it projects past the end of the board.
The starting point was a cheap dongle I bought from ebay for a couple of quid; luckily enough it’s based around the Ralink RT5370 chip, this makes it fairly straightforward to obtain drivers suitable for the Raspberry Pi. The first step was to take it to bits and see what I had to work with; this was achieved by bending a couple of tabs on the connector and slipping it off, after which the case pulled apart. No surprises here- a board with USB connection pads on one end, circuitry in the middle and an arial on the other end.