Duats
 

I've just came across this site and signed up for free and it looks fantastic!!

Is there a catch or is this just another example of how much more GA friendly our friends in the US are?

No catch, theres Duat and Duats, both of them for weather briefings and flight plan filing, provided you are in the FAA database.

I signed up today and although I'm based in the UK I fly in the states on a regular basis. I'm amazed that this service is free.

Very good service, very impressed. :D

A free alternative is FltPlan.com Flight Planning & Flight Tracking for General Aviation..

You have to register and then authorise them to submit flightplans on your behalf but that's a once only item. Very, very useful service. I've been using them for 6 years, both privately & commercially ie part 91 & 135 operations.

Many aircraft types are already in their database so once you enter the types & callsigns a lot of flight planning becomes a point & click affair. Similarly weather/notams for a flight or series of flights. They helpfully note planned UTC dep. & arr. times on the weather briefing which makes looking for applicable times within TAFs a no-brainer. For a fee they can even handle the US Customs' eAPIS notification for international flights and Safety Management System requirements (if that applies to you).