A couple of my really good friends now run tour businesses, and I can really recommend either Denis or Angeline depending on what you want to do, and how far you wish to travel away from Goa.
Denis is the owner of Stringfellos shack, and also runs a day-trip business. His friendly drivers will take you out into the countryside in modern open-sided 10-seater jeeps, to visit the spice plantations, or the waterfall at Dudhsagar, or many of the Goan Hindu temples. If there are enough of you he will customise a trip for you over one or more days. Have fun!
My old friend Angeline runs this new tour company. Her office are really conveniently located in central Candolim, and I know she will do everything to make a trip outside Goa special for you. Check out the Goa Footprints website here.
Angeline can arrange anything from local Goa day trips, to week-long journeys to Rajasthan or the Taj Mahal. She can also do other regular travel agent stuff for you like re-confirm flights, book train tickets and reserve hotels for you.
If you want an amazing couple of days away from the beach ask her to book you into Wildernest, a hilltop paradise on the border between Goa and inland Karnataka. She particularly recommends a visit there during monsoon, when it is like living in a cloud of mist.