There are quite a few programs to buy where you hook your midi keyboard/synth up to the computer and complete a piano course. I bought Voyetra's Teach Me Piano and got about half way through and gave up. Why? Because I found myself practising a lot of exercises I did not enjoy. Most are classically based.
But computers are great for learning to read sheet music. For six weeks I visited
http://www.emusictheory.com/practice.html and did the first three exercises (drills) for about an hour a day. Eventually I wasn't getting faster or more accurate - but I could vaguely read simple scores.
Next it was on to real music. The best thing I find is to get midi files (there are millions of these and plenty of gospel) and drop some into notation software. (I use Music Masterworks - a friend has Sibelius which is great but v expensive.) Then you can print out the score and practice and the software can play it too - good for checking mistakes.
But for theory and to expand your chord knowledge I think books are very helpful, particularly jazz ones. The Jazz Piano book by Mark Levine is excellent. Hope this helps. Good Luck
