Go the Home Depot and look for the Intermatics mentioned above. The timers I have are 9x6x4" in a weatherproof enclosure. 240V. They are fairly simple to hook up but as also mentioned above, if you're not totally comfortable fiddling with these things then get someone to do it. Better safe than sorry. I think they were about $60 or so....6 years ago and haven't priced them since.
Al