You can buy Noggle Stones and The Whisper King at all the usual places, and a few unusual places as well.

Check out Wil Radcliffe's Amazon page here.

You can also buy both series from Barnes & Noble.
Noggle Stones
The Whisper King

Smashwords also has The Complete Whisper King series.

If you don't like to read, buy the Noggle Stones audio drama from Colonial Radio Theatre!

And don't forget to check out the Noggle Stones Role Playing Game from Sanguine Productions.