The major carriers have their own dispatch groups that handle everything. Pilot gets details from dispatch for review before dispatch files the flight plan. If you're a small carrier, you may "buy services" from various groups. Jeppesen has an entire department that is the dispatch team for charters and small carriers. BTW, getting FAA certified as a dispatcher is one path to a fairly good career, the exam is similar to the ATP. Check out details on the Jepp course:
http://ww1.jeppesen.com/industry-so...ercial/training/ground-flight-ops-level-2.jsp
There are others, of course, but this is the most obvious for info. Last time I looked into it, it was full time for 6 weeks, over $4K.