Another good website for planning is
www.fltplan.com. They're who the mob I work for use. We're a Part 135 charter company.
conditions:
You have to register but that's free.
Can plan flights & stores a/c rego, pilot names, print flight plans etc. The printed plan usefully has basic ATC freqs. for Dep & Arr. aerodromes + FBO ph & freqs.
Access weather, TFR info, fuel prices etc
Can submit *IFR* flight plans to ATS *but* you need to go through a process to authorise them to submit on your behalf. Easiest if you already have an FAA 'duats' account (also free).