I hope though that the following links, and the links that spin off from them, are helpful as a starting point:
The British Council's Encompass Literature site has an interactive guide to fiction for ages 12-18 providing:
.. three reading compasses for Reality, Imaginative and Pot Luck. Within each compass you have between four and twelve subgroups to choose from, once again you can combine two groups to be more specific if you like. These include animal, magic, adventure, fantasy, humour, contemporary issues, classics, poetry, sport, self-discovery, family, friendships amongst others. If you prefer you can just search for Prizes or Interest Level in each compass. You can also use the Young Adult’s discussion board and join in the chats.The Centre for Adolescent Reading (CAR) has very useful suggestions as well as reviews written by teenagers.
The Young Adult Library Services Association (YALSA) has a whole lot of useful links to reading lists in different genres.
teenreads.com has a colourful website featuring useful reviews and a newsletter. I loved their Ultimate Teen Reading List, which I think provides a useful bridge to adult fiction (always a tricky transition).
BookSpot provides links to several other websites with useful information about teenage fiction.
And the Seattle Public Library has several useful booklists for teens including The Top 20 Young Adult books for the 20th Century.
Would be very grateful for your suggestions for other really good titles for young adult (that you've enjoyed, that your kids have enjoyed) and links to useful websites. (I know there are a few librarians who swing by the blog now and again, and maybe they're really the guys to ask ...)