Maya Island Air has two daily flights to and from Cancun to Belize City. And if you go to Dangriga, definitely check out Thatch Caye Resort. They are the most beautiful resort out in that area and also the closest to Dangriga.

There is a new bus tour company that has buses running to Belize for shopping and various other sightseeing and adventure tourism, take a look at their site www.playabus.net, it leaves from either Cancun and Playa Del Carmen and all the tours can be customized depending what you need.

Update...

The Maya Regional Air flights between Cancun & Belize City are not currently operating. They might start again in November.

ADO are currently doing some trial express bus runs between Merida & Cancun and Belize City. Full commercial operation is expected to begin in October. These buses will not go to Chetumal and will probably run at night to avoid direct competition with the services currently offered by Belizean buses.