I've written previously about different ways of visualising transit on a map, including commute time, in my post visualising city transit layers.
Some Twitter buzz today and recently about Mapumental mashing up public transit open data with properties available to buy and rent - effectively letting you search for homes within a commute time range that you set.
It's actually been around for a while with just travel times.
The property part is new.
Here's the map with just commute time (20 minutes to arrive by 9am at SW1A 0AA which is Westminster, the UK Parliament)
and here's the map with available homes to rent overlaid
You can check it out at property.mapumental.com
or the specific one I showed is http://property.mapumental.com/map/SW1A0AA-a-0900/44d71ed3