Items that make the amateur astronomer's life much easier.
A simple device that when placed at the front of the telescope shows very accurately when the 'scope is properly focussed. I use it together with the excellent freeware Bahtinov Grabber.
Hotech Laser Collimator
Used to collimate Newtonian telescopes (proper collimation is vital for sharp imaging). Provided that the telescope's primary mirror is centre spotted this device lets you collimate very quickly and easily.
PoleMaster Polar Alignment Camera and Software
A very effective tool for polar aligning equatorial mounts. It fits onto the mount using a supplied bracket and lets you achieve very accurate polar alignment in under 10 minutes.