Wunderground my favorite for weather. There is a radar feature in there as well, although I'm sure there are probably better "radar dedicated" apps out there.
Also, Windguru is great for wind. I use it via a bookmark on my iPhone though. Go into safari, go to the website, get your location setup, then save to home page.
I second RadarNow for no frills very fast loading. MYRadar takes a second or two more to load but has a higher resolution. It also has a nice wind overlay. Both are radar only apps, no weather forecast.