Depends what you want to keep up with.

Is it a development site awaiting permission?
Or does it have permission and awaiting building?

For the first, set a tracker on your LPA website.
For the second, register interest with the developer.

You can setup alerts on Right Move for when places come on the market in a specific area.

No covers the home counties too usually, commuter belts etc.

Presumably that only covers London though?

ES has something in the H&G supplement every week... probs the easiest way I would think?

Does anyone know of an easy way of keeping track of any upcoming new developments in a particular area?

Presumably I could just keep checking the planning permission applications, but I wondered if there's an easier way?