Indonesia forum

I'm assuming you're flying from KK to Indo... in which case you could do something like:

KK - fly to Jakarta
From Jakarta you could head out to Thousand Islands or south to Bogor, then back to Jakarta and take the day train to Yogyakarta for Boroburdur etc. From there continue east to Malang for Bromo-Tengger-Semura National Park (reallllly big volcano). From there onwards east again for crossing to Bali.

If you're looking for somewhere in west Bali to break up the trip, I can give a solid recommendation to Balian Beach area -- post back if you want more info. Otherwise, transit through for flight or boat to Lombok.

Spend a week on Lombok, then a week on the Gilis, then fast boat back to Bali, head to Ubud, then Denpasar and you're done!

All the above would fit in a month -- you could cram in Sumatra as well, but the trip would start to get pretty frantic...

Hope that helps!