Ok, so I tweeted this last night, but I ran out of room so here goes a more comprehensive explanation. I have 6 on my bench that I use for various things.
-Iodized - my wife uses this, I can't stand it.
-Kosher - I use for general seasoning.
-Fleur de Sel - I use for seasoning meats, chicken, etc. before cooking. Generally more flavorful and I use about 30-45 minutes before cooking the whatever I use to season it with.
-Celtic (Grey) Sea Salt - Excellent to use when seasoning steak or pork for the grill. The 'impurities' or minerals actually impart some great flavor to the meat. Allow this to sit on the meat while it comes to room temperature then grill. Awesome. First learned about this stuff in Spain about 10 years ago.
-Pink Salt from Australia - When we lived in Australia, the show 'My Restaurant Rules' had one of the participating restaurants was walking distance from our home in Manly, NSW. It was called 'Pink Salt' and used this liberally on seafood. Also good on beef or pork.
-Black Salt (Smoked) - this goes well beef and provides a good smoky flavor to the meat. Not quite as good as smoking or BBQ, but works in a quick pinch. Word of advise with this one - double bag it in two ziplocks and store in the cupboard, otherwise you will constantly smell it in the kitchen.
There are many others out there to experiment with but I hope this helps!
AustinEpicurean.com