Cambridge isn't blessed with the greatest of venues, but it's the crowd that makes a night really isn't it?
The Junction is the largest venue hosting regular techno nights. Located off Cherry Hinton Road, they have their own website. Tickets for events at The Junction are available from there, the Cambridge Box Office on Bene't Street or online, although you'll pay a small booking fee if you get them from the latter two.
Kambar formerly Route66 is to be found on Bene't Street in the centre of town. Small but recently refurbished (personally I was rather partial to the black paint and dive nature of the place). Club prices for drinks so those Red Bull vodkas are going to cost you.
The Devonshire Arms on Devonshire Road, off Mill Road city-centre side of the bridge. The Dev has been a music venue for years, with something going on most nights; reggae, ska and some sort of electronic stuff usually on a Thursday.
The Man on the Moon on Norfolk Street, off East Road. Still the main regular venue in Cambridge for hardhouse & trance nights, something on most Fridays. Website at http://www.manonthemoon.freeserve.co.uk
The Portland Arms on Mitcham's corner has a room out the back where events are held. There's something on every night, primarily bands including local folk clubs, but there're also regular and one-off DJ nights such as the regular electronica night Bad Timing. Well kept beer as well. See their website for listings.