There were actually several series that the Pythons were involved in other than the Frost Report. Most of these also involved members of the Goodies and other Oxbridge comedy teams. The main ones were

At Last The 1948 Show - A sketch show featuring John Cleese, Graham Chapman, Marty Feldman and Tim Brooke-Taylor (Cleese and Brooke-Taylor also appeared in the radio show I'm Sorry I'll Read That Again, which is where the Ferret Song heard on some Monty Python recordings comes from.) The Four Yorkshiremen sketch heard on the Monty Python Live At Drury Lane album comes from this series.

Do Not Adjust Your Set - A children's TV show featuring Eric Idle, Michael Palin, Terry Jones and the animation of Terry Gilliam. Also featured regular appearances by the Bonzo Dog Doo-Dah Band, and had David Jason in supporting roles. Probably the most popular of the pre-Python shows.

The Complete And Utter History Of Britain - A show that only lasted a couple of episodes, written and performed by Jones and Palin

Also the various members of the team were writing for shows such as Doctor In The House and Marty! at the same time.

Most of this information comes from the excellent book From Fringe To Flying Circus by Roger Wilmut, which covers the early 60s English comedy boom remarkably well.