Got one for my 40D - put me back about £35 including postage across the world. Really simple to use as you just plug it in the remote shutter release hole, no need for the laptop. You set the timer and interval between pictures on the remote timer (mine will take up to 400 shots on any settings). Set the camera to P or Av and let the camera take care of exposure.
Don't know how fast or slow you want your timelapse to be. Main thing is can allow your camera to go to sleep between pictures (the timer will wake it up for the photo), so if you shot one pic a day battery and card would last for months.
Alternatively, one shot every 4 minutes on my timer would cover an entire day and night (don't sleep in the same room). Then each morning you'd could press the stop/start button on the timer to make it take the next 400 photos. Or do one shot every 1.5 minutes to cover 10 hours around working day and daylight - then restart it each morning!
At that rate you'll need to change battery every three days or so - and either shoot JPEG or be downloading cards every day too.
What I've done to make a movie with the pictures is use slideshow software - most have a free trial download (I use slideshow gold). Using small JPEGs (1000 pixels longest side) the slideshow will easily cope with showing the pics at 0.1 seconds each and no effects (most have 3 second fade set as default) and it looks like a movie. One day of 400 pictures would last 40 seconds! You can even make a little .exe file out of it to fit on a memory key or email to show friends.
Hope that helps.
Sue
