+2 on a fridge and heater combo with a dual stage controller. It's not the cheapest option, but you really can't go wrong with this setup and you certainly can't beat the accuracy in temperature control you can achieve. Just set it and forget it, and rest assured that your fermenter temperature is exactly where you want it to be (although do make sure it works properly before you put your first batch into it).
I live in Phoenix where the temperature in my garage (where I keep my fermentation "chamber") can swing from the 40's (at night) to the 90's (during the day) repeatedly over the course of a three week fermentation this in the spring and fall.
I use a dual stage Ranco controller with a little Sanyo fridge (just big enough to hold a carboy or 6.5 gallon buket) and I connect the 2nd stage heating plug to a fermiwrap heater that I have taped to the inside. This setup (with the temperature probe in a thermowell within the fermenter) brings my primary temperature down from 80 (after post-boil chilling) to my typical fermerntation temperature of 68 degrees in less than 3 hours, and with a 1 degree differential programmed into the controller, it will hold that exact temp (+/- 1 degree) without any issue at any time of the year without any need to fiddle with the programming. I verified this using a cheap wireless thermometer (which I put in the "chamber" where the receiver shows the high and low temperture over the last 24 hours on day where it got as cold a 48 at night and as hot as 88 during the day in my garage. Lowest temp was 67: Highest temp was 69. Granted, during the summer when my garage gets up over 110 degrees, my fridge runs almost constantly...but this setup still maintains the temperature.
Look on craigslist for a compact fridge (widely available for $50 or less), throw in your heater (~$25)/ temperature controller (~$120), and you should be able to put together a similar setup for under $180.
