New rider links
http://www.sportrider.com/ride/new_rider_guide/ - New rider & 'first bikes' guide - also has some tips for more experienced riders. Worth a browse, IMHO
Streetbike links
http://www.bikez.com - As the title says, bikez!
http://www.uponone.com - stunts I guess
http://www.motorcyclenews.com - UK bike news and buy/sell site. MCN is also the top UK bike magazine.
http://www.motorbikestoday.com - UK online bike news
http://www.sportrider.com - US Sportbike (magazine) website
http://www.usedbikeguide.com/guide/index.htm - UK used bike guide (magazine) website
http://www.motorush.com - Informational bike forum, reccommended by RC45
http://www.motorcycle-usa.com/ - News and reviews
http://www.motorfreaks.nl/ - News and reviews (In Dutch)
Dirtbike links
http://www.thumpertalk.com - Ultimate 4 stroke dirtbike resource
Manufacturer-specific links
http://www.suzukicycles.org/ - A database of ALL Suzuki motorcycles ever produced, kudos to Jarmo Haapamäki of Sweden who runs this site, it is very useful!
If anyone can find similar sites to this one for Yamaha, Honda and Kawasaki it would be verymuch appreciated
Buying and selling
http://www.cycletrader.com - Autotrader for bikes.
http://www.cycletrader.ca - the same for our Canadian readers
http://www.biketrader.co.uk - the same for our UK readers
http://www.mobile.de - Trade bikes and also cars. For EU/German bikers
http://www.motorky.com/ - for Czech bikers
Feel free to add to this thread, and I will edit this post to add new links