My DS loved the Tiny Love classic mobile, really colourful with a nitelight and 3 different melodies with 2 volumes. We have only just taken off the mobile arm when he reached 8m but the actual music box is still on his cot and he loves it
I just posted an answer to a similar question on another thread, so thought I'd post it here too.
The Fisher-Price Precious planets one is great. When they're little, you can have the light show projected on the little canopy with animals dangling down, and then when they're older, you can take the canopy off and it projects (well) on the ceiling. At the moment, we're in limbo because the animals were being pulled off, but DS still likes the canopy, so it spins round without the animals now. It have two volume options, as well as 3 classical music options, 2 nature sounds and a heartbeat option, which I always use in the middle of the night and even though DS is now 7mo, he still finds it really comforting and not at all distracting because the lights can be turned off if desired. We actually got it when he was 4mo and I thought that it might be 'too late' to use the heartbeats, but not at all!