The www.ratbike.org forum has got an old-school, clunky interface, but if you want to talk with knowledgeable people doing strange things with motorcycles; swaps, hacks, diesel conversions, etc, then this is a good place to look:
http://www.network54.com/Forum/598839/
These blogs do features on custom bikes with short write-ups on their construction and whatnot:
http://www.bikeexif.com/
http://thekneeslider.com/
http://www.customfighters.com/blog/
The following are just some blogs with "hey thats a neat bike" photos. Some have links for more info, while others are just the photo and no info. Also note that some of these sites are known to post tasteful pictures of topless ladies:
http://ottonero.blogspot.com/
http://www.8negro.com
http://customfighterspain.blogspot.com/
http://shinyakimura.blogspot.com
http://sideburnmag.blogspot.com
http://rocket-garage.blogspot.com
Look down the right side of any of the above blogs to find a long list of other, similar blogs. You should find plenty of interesting stuff to waste your time reading