Hi
Melakka is a really nice place. It has a quite a lot of old historical buildings, and is really a charming place. Its a mixure of China (old chinese houses), venice (some kanals), indian food stalls, portoguese colonial buildings, malay moslem architechture and food. Its quite touristy but well worth it.
Otherwise I would suggest going to Pulau Tioman. You can fly there from Singapore or get on a "fast boat". A beautiful island for swimming, snorkelling, diving....