Terracotta pot heater
This idea comes from the petsnails.co.uk-forum where a member saw it being used on Animal planet.


What you need:Terracotta pot (17 or 19 cm,smaller is possible too but the surface of the pot will get very hot),2 dishes to fit 
at the bottom and top,electrical cable,plug,lightbulb fitting(try to get one with a L-shaped bracket)lightbulb 25W,superglue,
2 pieces of wood ca 7 cm.
Tools needed:powerdrill,hammer,saw,screwdriver,wirestripper or knife.


How to build it:
Attach the plug and the fitting to the cable.You can also attach a switch to make things easier.
Screw the fitting with the L-shaped bracket onto one of the pieces of wood.
Glue the wood on the inside of one of the dishes.
Use the powerdrill with a stone-bit to make a groove at the top of the terracotta pot(the widest part).This is for the
cable to fit in.
Use the hammer to widen the drainage hole on the underside of the terracotta pot.
Measure the opening you now created and saw a piece of wood to that size.
Glue the piece of wood to the underside of the other dish.Try to see if it fits.
You can now easily take of the dish if you need to replace the light-bulb.
Glue the terracotta pot to the dish which holds the fitting.
  


What it costs:
That depends really,most of the materials used you might already have laying around in the house.But if you have to
buy all the materials new I would say less than €10.00 or £7.50.


Alternatives:The heatmat of course,but since those are quite expensive this idea is such a good one.Especially because it doubles 
as a humidifier.
Lamps:Another good,additional,heating source are lamps.There are special reptile ones on the market,but
ordinary ones work just as well.Some research will be needed,however,into all the different options:
infrared,daylight blue etc.