Metcheck.com : Now primarily a commercial site, it still offers some useful free info. especially for general weather trends up to 30 days ahead.

UK Weather Latest : Latest update from the UK Met office via the BBC news site, this link offers a very recent update on where it is raining, and where it should be dry.

Weather (lightning/radar) Online : This offers a good idea of where you'll find severe lightning storms, updates every 30mins.

Tornado and Storm Research Organisation : A very in-depth site, independently run.

Severe weather map (Europe) The very latest met map of storms across Western Europe. Updated every 30mins. Data from meteocentre.com

USA radar latest : The very latest from America, current state of the nation rainfall. Also, links to severe weather in all 50 states.

Accuweather forecasts : Via yahoo, this site offers much more than any site I have found yet. Accuweather are a commercial weather company based in America. However, they provide extensive  information about the worlds weather.
*Special note here for Joe Bastardi : one of the best forecasters ever, both funny and a real smart ass. Check out his 'long ranger' forecast, which he updates daily and looks up to 2 weeks ahead, even longer in some cases.

USA Weather : A comprehensive in depth site, includes links to MRF and other long range pressure forecasts.
 All data provided by Unisys

British Storm Watchers Community : using the MSN communities, this is a great new group, dedicated to bringing together like minded storm chasers across the UK.

Weather sites central : A great place to find a wide variety of locations covered by weather enthusiasts.

www.bylink.com : Covering the Leicester area, central England.