Colombia-one of my favorite countries: beautiful, cheap, great weather, interesting culture, ruins, beaches, reefs, beautiful people....what more could you want?!
Bogota-a little sketchy (cocaine is quasi-legal and super cheap), but if you can speak even decent Spanish, you'll have a great time.
Zipaquira-a nice day trip outside of Bogota where you can see one of the world's largest cave cathedrals! Also had one of the best meals of the trip: soup (delicious), rice, beans, vegetables, plantains, meat, beer, dessert for $1.50. It was so cheap I thought they had made a mistake!
Villa de Leyva: one of my favorite spots in South America
San Gil: gateway to epic whitewater rafting
Barichara: colonial gem in the mountains
Santa Marta-gateway to Tayrona
Tayrona National Park
Islas de Rosario (near Cartagena)
Zona Cafetera-Hacienda Guayabal