Conrad UT-200 - Basic thermostat driven outlet [Sensor type: Analog NTC (103AT-11)]
This is a simple outlet driven by a thermostat. You specify a minimum and a maximum temperature to trigger the outlet. It is only suitable if you want to either cool or heat. Otherwise you'll need 2 of these. You don't need to do any wiring as it is plug-and-play. Beware: the cable of the probe is prone to breaking where it leaves the chassis. I recommend to fixate it using a drop of hot glue. Also, at about 40 EUR it is pretty expensive in comparison with other options.
STC-1000 - The Chinese temperature controller for heating and cooling [Sensor type: Analog NTC (NTCLE413E2103F102L)]
A widely used temperature controller for both heating and cooling. It is available under different "brands" but the main look is always the same (dark gray body with orange mounting brackets). I've a pair that are branded "Elltech". You will need to buy some additional items to get the wiring done: 2 sockets, 1 plug and some wires. At less than 20 USD (including shipping) these are cheap and at this price it makes sense to buy a spare one too. You can find them on eBay, AliExpress etc...
There is a project on GitHub allowing you to flash the controller with a custom firmware which allows you to create temperature profiles. The flashing is not for everyone as you need some additional hardware and basic electronics knowledge. I will attempt to flash one of my controllers in the coming week and leave a report on the forum.
BrewPi - An open-source temperature controller/logger. [Sensor type: Digital (DS18B20)]
If you want very accurate temperature controlling and/or good logging of you fermentation temperatures, you might want to look at the BrewPi. The core of the BrewPi is an Arduino with a custom BrewPi shield. The Arduino/shield combo monitors and adjusts your fermentation temperature. If you want you can hook it up to a Raspberry Pi or a PC with an USB port. The RasPi or the PC runs a web server (Apache) with a web application and a few scripts (Python) that function as a data logger and administration page. You can check and adjust your fermentation temperature from anywhere in the world if the RasPi/PC is connected to the internet.
Since the BrewPi is using digital sensors and a PID algorithm it is very accurate. All software/hardware is open source so you can alter it if you want. This is also one of the more expensive options. You pay about 98 EUR for the assembled shield with 3 probes and 2 SSRs (without shipping). Add the price of an Arduino Leonardo (about 22 EUR) and a Raspberry Pi (about 25 EUR) and some small pieces (SD card, power supply, USB cables, ...) and you'll reach the 200 EUR mark. This doesn't even include a enclosure...
BrewBit Model-T - A to-be-released open-source temperature controller [Sensor type: Digital (DS18B20)]
I added the BrewBit Model-T to the list because it looks promising: open-source, nicely enclosed with real sockets instead of screw terminals (BrewPi). Pre-order price is $189 USD. It looks like BrewBit will be shipping out the first units in the coming weeks. It looks like they are working on a specific gravity sensor too...
I've been working on a temperature controller/logger using a NetDuino and the .NET Micro Framework for about 2 years now. But since the last 2 years were about the busiest period of my life I didn't get further than 2 working prototypes with a few successful logs. One day I will complete this project

Feel free to add your favourite temperature controller/logger to the list.
Niels