It sounds like you have done the simple checks, and if you get a hum from touching the jack that rules out cable and amp (aside from a couple of exceptional faults.)
Do as Todd suggests, and try turning the knobs full range while the cable is plugged in and seeing if strumming generates any sounds from the amp. Also check to see if any of the pots are pull/push.
Next step is to unscrew the plate holding the jack socket on to your guitar. This varies between guitar types, but is often a small metal plate with a couple of screws, like this one from strat-talk.
When you pull this carefully away from the guitar, you should see two wires connected to it - the most common things that go are either that one of these has come loose or the springy bit has bent back and no longer touches the jack.
If it looks fine, the next thing to check is wires going to your volume and tone pots - these may require a different plate to be unscrewed; sometimes it's the scratch plate, sometimes you get at these from the back etc., but again, you are looking for a wire that isn't connected any more.
Soldering wires back on is straightforward if you have done it before, but if not, the thing to remember is that soldering a wire to a chunk of metal (like the output jack) requires the metal to get quite hot in order to make a good connection, so be careful. If in any doubt, take it to your local guitar shop.
