I posted one of these a few months ago and it sold out before many managed to get decent prices, but it's back again:
"Early booking has its own rewards: when you choose to book one of our South-American destinations before Tuesday, you can fly during May and June 2011 starting from £389*. Immerse yourself in times past while wandering through Bogotá's picturesque old town, be enchanted by the rhythm of the tango in Buenos Aires or relax on white Caribbean beaches in Caracas."
Bogotá from £399
Buenos Aires from £459
Caracas from £429
Don't forget Topcashback @ 2%!