Swamp Cooler
The swamp cooler is a cheap way to lower your temps by up to 15ºF in my experience. It is not accurate and makes a bit of a mess.
Cost:
Tub - $10.00
Insulation lid - $5.00
Ice - free
Total - $15.00
Pros:
Very cheap, you probably have everything you need already
Can lower temps
Requires no knowledge or skill to construct
Cons:
Messy, it is called a swamp cooler for a reason
Cannot accurately control temps, control is achieved by adding more or less ice, by using a fan, or a couple other ways
Refrigerator with Temp controller
An upright fridge with a temp controller installed is a nice option but requires more funds and more fab skills.
Cost:
Fridge - $300.00
Controller - single stage - $56.00 : Dual stage - $70.00
Misc. Wiring - $20.00
Total - ~$400.00
(You can ALWAYS find an upright fridge on CL for free if you have some patience. See my side-by-side conversion in my sig. My setup cost $100.00)
Pros:
Upright format allows easy access to fermenters without a lot of lifting
Exact temperature control across a full range of temperatures (ales, lagers, conditioning)
Large capacity if you use a big fridge, I can fit 8 carboys in mine
Can position fermenters at a height so you can siphon into a keg, secondary, or bottling bucket without moving fermenter.
Cons:
Requires more technical knowledge and the ability to do some electrical work
Costs more than a swamp cooler
May be less efficient than a Freezer conversion
Freezer with Temp controller
The chest freezer can easily be converted to a keezer for serving beer and double as a fermentation chamber. Installing a collar is easy.
Cost:
Freezer - $300.00
Controller - single stage - $56.00 : Dual stage - $70.00
Misc. Wiring - $20.00
Total - ~$400.00
(Like uprights, you can ALWAYS find a chest freezer on CL for free if you have some patience. My keezer without the taps cost about $100.00)
Pros:
Exact temperature control across a full range of temperatures (ales, lagers, conditioning)
Most efficient because the colder air stays in even when you open the door
Easy to make a collar
Can be used for serving and fermenting
Large capacity if you use a big freezer
Cons:
Requires technical knowledge and the ability to do some electrical work
Costs more than a swamp cooler
Difficult to lift fermenters in and out
cannot siphon in position
Son of a Fermentation Chiller
These are the most work intensive but can be built custom so you could potentially keep it in the house (see the Fermoire). Most expensive and require the most technical expertise. This is the only type I have not built (sorry).
Cost:
There are infinite way to do this. The cost really depends on what you intend to make. I think most units shown here and elsewhere have been in the $400.00 range.
Pros:
Made custom so it has as much insulation size and cooling capacity as you want
Cons:
You have to build the entire thing and supply it with fridge internals or use ice for cooling. Ice requires continued maintenance.
Maybe others can add to these things....