Bleh, all the weather and radar apps suck. Since we now have flash and can do animated radars in browser go to firefox on a pc and find the radars you like from different sites (wunderground is my fav). Right click background of web page and tick web page properties and find the media protion of the site and grab the url for just the radar image you want. Also it's best to set up the radar in the page before grabbing the url i.e. animation and zoom levels and other features. So I'll have multiple links for different zoom levels and different radars.
And you will end up with a custom radar that you can bookmark in browser without having to load an entire web page.