I recently completed a mechatronics project for school using an Arduino Uno to heat and cool a son of a fermentation chamber I built. The cooling is done with the usual fan/ice method.
My initial thought was to use lightbulbs for the heating portion, however, I found flexwatt from this site http://www.bigappleherp.com/Flex-Watt-Heat-Tape
and think it works great. I think I purchased from a cheaper supplier. I can get the chamber and 5 gallons of liquid up to 100˚F from 65˚F overnight on full power. The PWM pins work great if you want to hit a specific temp and maintain it...little bit of trial and error with that. Great if you're in the basement/garage or using lacto cultures or something. I used one of the cheap Fotek SSRs for this, like $10 on amazon and cheaper on Ebay if you don't mind the wait. The flexwatt only pulls about 40W and like 3A so it is pretty energy efficient compared to the bulbs.
For temp sensing I used TMP36s which you can find at SparkFun and they are really inexpensive and easy to setup and get working. The project now stands alone and has buttons to increase and decrease the set temp and has and LCD display for read out of set and actual temp and whether the fan/heating element is on.
I knew nothing about microcontrollers before beginning on the project so I kept it pretty simple and added different components in stages. Sounds like you're doing a similar project with similar experience so let me know if you would like any help with code/setup/ideas etc. No ethernet yet, but that's my next step.
Just my $0.02. Best of luck and have fun!