After.
If your cabinets are custom, have the cabinet shop make them with a 5" toe kick.

If they are bag-n-box, have the installer hold them 3/4" above the floor.

This will eliminate any potential difficulties with the installation of undercounter appliances.

Lay the floor before. You will have a better, all around finished product in the end. You will spend a bit more, but if you ever want to change anything you will be soooo happy that the floor runs all the way under the cabinets.

Lay the floor before and have the contractor fill in under the cabinet area with pine boards or plywood whichever meets the height of the floor. Just have the finished floor extend a couple of inches under the cabinet. Thats what I would do. Saves some money and you end up with a better laid floor. After its down make sure he puts a floor protector over it so it doesn't get scratched when he installs the cabinets

Last year when my house was gutted and remodeled, the new oak floors were installed before any cabinetry was installed. Oak runs wall to wall in every single room in the house, including bathrooms and closets. The floors were not finished, however, until after the cabinets were installed and all of the painting was completed throughout the house.

James

Always, if possible, floors first.

Hmm I would say first for tiles etc, but for a lay down click or slot or whatever you want to call it, floating floor, I'm told you should NOT run the flooring right under the cabinets. I was told this by my ex boss who was a moron in many regards but knew what he was talking about in this regard. Apparently you get too much movement if the cabinets sit atop this type of floor.

He recommended that you lay the floor AFTER, also eliminating risk of damage to floor, naturally you have to make height allowances, but get kitchen installers to leave the kick panel off - then you have open space under cupboards. Flooring is laid up to - but allowing space around - the plastic leg things that hold kitchen cupboards up these days. Then, once floor is in place, kickboards are put in, so they run flush to the floor.

They look just as good as floor will continue some distance under kickboard, but your cupboards will be sitting on a solid, stable floor, where they won't move - movement would cause problems with your splashback joints and possibly with any tiling.

OK two things:
1. If you have a prefinished floor and you put it down first before cabinets and other finish work, MAKE SURE you protect it and preferably with something thick enough and strong enough to deflect dropped tools.
2. I've also heard that you should not place cabinets on top of floating wood floors, because by securing the base cabinet so it doesn't move, you prevent the wood floor from expanding and contracting. Can anyone confirm this?
Actually three things :-):
3. We have a concrete slab subfloor. Is it okay for the cabinets to sit on this, since it sounds like we're not supposed to place them on top of the floating wood floor. Also, how do you get the appliances to slide out? Do you need to put plywood underneath them?
OK, so maybe that was more than 3 things....

We are remodeling and our GC put the oak floors down first, even before the painting and granite installation.

Pchow,

You are spot on - you should build the floor under cabinet space, at least where appliances go, with something of similar thickness to final floor - plywood'd be ideal. Personally, I'd seal it with something too.