As far as corporate guys go, we pretty much have to fend for ourselves - but we have a lot of good help. Our company operates 4 jets and a turboprop. We have manufacturing plants and/or facilities in all 50 States, Canada, Mexico, Europe, South America, Japan, Australia, and New Zealand so we get around quite a bit. The method that we use to flight plan depends upon the flight's origination and destination. For flights within the continental US (including Alaska) and Canada we usually use Flitesoft. For all other flights we contract with Universal Weather for handling, weather, and flight planning services.
Flitesoft is a great program and it's VERY easy to use once you get the hang of it, but at first it can be a bit intimidating. You basically enter the departure and destination airports; check for appropriate SIDS, STARS, and Preferred Routes; then you simply "connect the dots" for the enroute routing; add passengers, baggage and fuel and tell it to call up DUAT and download the winds, weather, NOTAMS, etc. It then gives you the time and fuel burn for 5 different flight levels appropriate to the direction of flight. At that point you simply select the "best" one and click another button and the flight plan is filed. Total time required to plan, file, and print the navigation documents for a coast to coast trip is maybe 10 minutes. As far as accuracy goes, we regularly fly from our headquarters in Klamath Falls, Oregon to one of our plants in Orlando, Florida. Flitesoft typically will be within 3 minutes on our enroute time and 100 pounds on the total fuel burn. I've had several trips where the time was exact, to the minute and the fuel was within 1 gallon! (I know that it was a fluke, but we have to have something to bet on to see who buys dinner.) For our oceanic and international flights, Universal Weather provides all of our flight planning needs. We just tell them where we want to go and when we want to be there and they handle EVERYTHING. It's the only way to fly.