Well, two ways that I look at salmon is 1.) it's a very oily fish, and 2.) it is a fish with a very robust flavour.
Any time you can add acid to something oily, it usually ends up pretty good, and even quite refreshing. So lemon is pretty popular with salmon. Balsamic as well.
However, also because it has a robust flavour, I think it works well with other very powerful flavours, such as mustard, whiskey, or maple syrup.
I always grill my salmon, as I don't have a decent frying pan that will allow me to pan-roast the salmon properly. If you grill a filet, make sure you grill it flesh side down first. If you grill it skin side down first, and finish on the flesh side, the flesh will be cooked when it's time to take it off the grill, and the fish will flake quite a bit easier. So when I grill the salmon, it's rubbed with olive oil, salt, and pepper, then placed at a 45 degree angle on a very hot grill(well I wouldn't say "very" hot, but quite hot. It should sizzle when you put it down). When it comes time to flip, I give it a gentle push from the side. If the fish doesnt move freely, don't force it. Let it sit for another minute, then try again. When the fish has the proper grill marks, it will release from the grill surface easily, then you can flip it.
Then I do one of three things. Either finish it on the grill, and put a simple squirt of lemon juice as it's coming off the grill, as well as another little sprinkle of salt. Or, I'll glaze it with a maple-dijon-whiskey glaze as it's finishing on the grill. Or I'll make a classic beurre-blanc sauce, usually with lemon, and dill.