Just on to rave a bit about the Gro-Clock I bought a fortnight ago. It's blooming brilliant!
The basic idea is that it is a night-light with built in digital alarm clock. In the day it has a sunny yellow face and when you send it to sleep it turns blue with stars. You set the wake-up time for the morning (or daytime nap) and the blue changes gradually back to the sunny day colour at teh appropriate time (it can do an audible alarm too).
My DS was 2 the week it arrived and had decided that sleep is not for him 
we had a few battles going to bed (11pm and still running round the house) that we pretty much sorted. Plus tired or not he wakes at 6:45 when DH tiptoes into the bathroom.
Since we have had the clock he has gone to bed much more easily - "See the stars - it's night-time!". And in the morning, in the 10 days since we have had it, not one day has he woken up or shouted before 7:30!! On Saturday I even sneakily set the nap-time setting to 8:30am and had a lie-in!
This morning I went up at 7:45 as I thought he was still sleeping and heard "I awake". He was sitting looking at the clock.
I recommended it to someone at work last week and they told me this morning that their toddler usually wakes at 5am but since the clock arrived has slept until the "alarm".
How marvellous is that?? I'm a bit of an evangelist about it now (although not on commission sadly). Anyone need more sleep in the morning???
(Oh and I bought mine for £17.99 in a sale on Amazon so shop around to see if you can get a cheaper one.)