Opening up a can O' worms...

If you don't currently own a wormery I strongly recommend you get one. I've had mine for several years now and use the finished compost (called vermicompost) in most of my potting mixes. It has many benefits but the two i'm most worried about are 1) It significantly boosts the beneficial bacteria (microbial activity) in the compost/soil which makes for a healthier plant and 2) It increases the water retention in the compost whilst still maintaining a free draining medium.
Anything that you put in a normal compost heap can go into a wormery- only in smaller quantities. You wouldn't feed a baby a three course meal so don't do it to your worms either! - they only have small gobs...
I add all our kitchen scraps, teabags, green weeds, straw ( to maintain the correct nitrogen:carbon ratio). Wormery manufacturers also say you can add bread an small amounts of pasta and rice but I never have in fear of attracting vermin. However I do add from time to time, chopped seaweed (ideal if you live near the coast), rock dust ( worms love it) and, in small amounts, manure ( rabbit, horse, guinea pig etc). Try to avoid pig, poultry or cow manure as they are either too wet or too strong.

This is the wormery I use. You can get it from wriggly wrigglers. It comes with everything you need to get started including bedding, food and worms!

If it looks like its too wet I just add a couple of handfuls of straw...

...and then mix it in with a handfork.

We have a bucket near the kitchen to which we put all our kitchen scraps etc. The straw at the bottom is to soak up any excess moisture from the scraps.

This is the good stuff ready to use. Often referred to as 'Black Gold' this is what I incorporate into my compost when potting on. Its teeming with life which encourage healthy pest-free plants.

 bucket is placed under the tap to catch what they call the 'Leachate'.  This can be used as a diluted liquid feed.

When you think that there are companies out there selling wormcasts at 12-13 quid for a small tub it's worth investing around £60 for a decent sized wormery so you can produce your own unlimited supply. After 5 harvests it will have paid for itself and everything after that would be a bonus!
Below is a link to the RHS webpage all about wormeries and what to add/leave out:
http://apps.rhs.org.uk/advicesearch/Profile.aspx?pid=726