The most durable (not safe to apply yourself) floor finishes now are the catalyzed water base finishes. There are three I can recommend; Street Shoe by Basic Coatings at http://www.basiccoatings.com. Then there is Traffic by Bona Kemi at http://www.bonakemi.com. And last but not least is the Dura Seal 2000 water based finish. They are all basically good finishes, and are used in gym floors and bowling alleys. The only drawback is their expense, and the fact that they have to be professionally applied (they have a very toxic catalyst agent). They unfortunately have a pale blue film color. Be sure you see some 5 year old jobs before you choose one of these finishes, they don't tend to age well, especially on dark wood.
There are other conversion finishes that are as durable, but they both emit very toxic fumes. In the case of the Swedish finishes, up to 90 days of urea formaldehyde fumes and moisture cured polyurethane contains lots of toluene.
But for a moderately durable (what I use on my floors) try 3-4 coats of a good oil modified polyurethane (Fabulon brand is all I use), or read the Article in the Floored News about the new Dura Seal 1000 water based finish. Both these finishes are fairly safe to use and much less expensive than the aforesaid finishes. And all these finishes will scratch, but the OMP will be cheaper to re-coat in the future. It's something you can use yourself.
As always your Most humble servant, Joseph, the Wood Floor Doctor.