WifiBar
Get it on Google Play
Simply puts a small icon at the top of your device showing the network you are attached to

This app helps you keep track of your WiFi connections by displaying a small icon on your status bar.

For example, the house icon above can be assigned to your home network
You can assign different icons to different networks.
A configuration screen will show all the networks you have previously connected to.

If you click on a connection you can assign an icon to it.

That icon will show on the top of your screen whenever you attach to that network in the future.

If you don't asssign an icon then the first two letters of the network name will show. For example, if your network name is 'home' it will show 'ho' as above

The trial version also shows a little thumbs up sign.
Lots of icons to choose from.