Lumicycle if you have a couple of hundred quid: great lights, great service, really tough bombproof stuff. I just got the halogen 12/20 LiIon set and am pleased as punch; my sister's been running similar with a NiMH for a couple of years. For lesser needs, Smart have some nice stuff out now with a 1.5-2h burn time.

For rear, just make sure you have two in case one dies. The CatEye TL600 - the long slim one - is very good, and rumour has it that the new TL1000 is the dog's bollocks. Anything big, bright, with a steady mode is good. If you're a regular commuter get rechargeable batteries.

Oh, correction on studded tyre wear: check the "studded tyres" thread. *Steel* studs wear out fast, but the Nokians with *carbide* studs last for years. Mea culpa... and mea empta (?) - might get a set as this looks like a good Dartmoorly winter!