I would have thought if you were in your 3rd year, you would be able to work out any circuit's function! There are very few sites that offer a circuit diagram and an explaination. Most offer one or the other, with the idea that you either require the design or the theory. Most people design a circuit from theory, or back engineer it to work out the theory.
If you ask me, I would find myself a nice looking circuit on the web; or better yet, as you are in your final year, think up your own circuit, and just study it for more than 5 minutes and work out what it is doing. The point of a final year project is to prove you have learnt all that they have taught you in the course. I suggest if you can't work out your own circuits by now you see someone about and not try and take the easy way out!