Good brands:
Crucial; Corsair; OCZ; Kingston; Cellshock
Some here favour Geil memory as well but most reviews I've read put them low down the scale, so I'm not sure.
And I don't know anything about Team Extreme or Overclockers UK own brand.
In general though, avoid generic makes, go for branded.
And unless you intend to overclock there's little point in buying the more expensive types, if you're running standard clock speed, Crucial's vanilla flavour is fine, you don't need their Ballistix type.