There's a couple of weather ones, at least. One called http://www.androlib.com/android.application.com-kelox-aviation-and-qDw.aspxAviation Weather, one called QuickWeather, and one called ForeFlight Weather.
ForeFlight Weather is made by the same guys who made the AOPA guide for the iPhone. I've been in touch with them, and they're going to port the guide to Android too, at some point. (The more people that bug them the quicker they'll do this, I think, so go ahead and give them a nudge.) ForeFlight Weather is $20 though, which is a bit rich for my taste.
I've only used QuickWeather so far myself, which is ok enough (Could use some UI polishing), haven't had time to try out the other ones yet.
I've also been in touch with the guy who made AirportStatus for the iPhone, sounds like he's going to port that app over here too, at some point.
I have been using foreflight for a couple of weeks now it works good. I really like Air WX app. it is easy to use and it has approach plates available and it stores them in the phone so they are accessible in flight....I probably wouldn't trust it as my primary source for plates yet but it is an excellent Backup. I would recomend both of them.
We've got a couple of aviation apps on the Android Market:
+ Aviation Weather by NOAA/NWS (FREE), which is basically just a convenient launcher for the currently experimental mobile version of aviationweather.gov (though if you're using Android 2.0 or later, we add a little extra functionality)
+ Aircraft Weight & Balance (free to try, currently $9.99 to buy) - details & screen shots available at Weight and Balance Calculator (Appventive). If you do give it a try, I'd love to hear what you think - either post it here or email me.
Just search for "Appventive" in the Android Market to find either app (the W&B calc is also available at AndAppStore.com if you don't have access to the Market app).