My office is in the University Computer Laboratory "William Gates building". This is about 1.5 miles from the centre of Cambridge, and 3 miles from Cambridge railway station. Directions and a local street map are available as a single page PDF file.
If you are coming by bicycle, I recommend that you avoid cycling on the Madingley Road, which is a busy traffic route with inadequate provisions for cycle safety. The bicycle route along the "Coton Cycle Path" is safer, far more pleasant, and worth researching. From central Cambridge, this passes along Garret Hostel Lane, Burrell's Walk, Adams Road, onto the Coton footpath, then Clerk Maxwell Road and left onto a brand new cycle path. The university provides an online map that can be used to plan this route.
Potential source of confusion: the William Gates Building is NOT the location of Microsoft Research Cambridge. The Computer Laboratory appears to be in front of the Microsoft Laboratory (physically). Potential landmark: The University Physics department, usually called the Cavendish Laboratory, is just beyond the Computer Laboratory. The Cavendish is better known to taxi drivers, as is the University Veterinary School, on another part of the West Cambridge campus.
Visitors from outside the department should ask for me at the reception desk immediately inside the front door. If you are a local, and allowed to walk around the building by yourself, my office number is SS10. SS means Second (top) floor South wing, as shown on this map.