It would certainly be nice to have the whole Tipitika on line. The project that David points to seems to have collected the material from Access to Insight and Mettanet, and is in the process of adding to it from out of copyright PTS editions, and other sources. Frustratingly, in many cases doesn't give the source, and appears to often omit the footnotes.
I would make a few points:
1. For serious study I prefer the modern translations from the likes of Wisdom Publications, http://www.wisdompubs.org/Pages/c_teachings.lasso
which have copious notes and introductory material.
2. It is most likely overkill to read all
of the Suttas, and I think we all fall into a desire to "own" the Tipitika. Somehow, if it was all on our bookshelf or on-line it would be "ours". Unfortunately, that's only a preliminary. For the last three years I've mostly studied the Majjhima Nikaya, because there are a lot of on-line resources available, such as Bhikkhu Bodhi's excellent talks. The $50 cost of Bhikkhu Bodhi's translation is completely trivial in the context of the amount of time I have spent studying it. I could probably usefully spend several more years just studying that one volume.
3. Where a complete on-line resource would be incredibly useful is where one is reading an article or book that refers to many sources scattered around the Tipitika and it's Commentaries, or when one wants to locate something by searching. I sometimes find myself searching on-line resources, then, armed with the reference, read it in the book. That can be much faster than using the paper indexes...