Good sites I have found...
http://www.303products.com/Cleaning and protection products for your boat
http://www.getaprop.com/Propellors - great service - even to me in Oz!
http://boatsafe.com/Boating courses and useful safety information
http://www.fishonmarine.netHuge range of marine electronics - great service and delivery to me in Oz
http://marinerv.meguiars.com/Premium marine and RV care with plenty of instructions and tips
http://www.iboats.com/Boats, parts and products. Plenty of useful information and forums as well. I have purchased from them and found them very helpful.
http://www.jandhproducts.comMarine electronics Superstore
http://www.dougrussell.comMarine engines, stern drives and parts. Very useful exploded parts diagrams that give detailed part numbers
http://www.boatengine.netInteresting discussion group
http://www.michiganmotorz.comMarine engines and parts
http://www.overtons.comBoating accessories
http://www.ram-mount.comMounting solutions for all of your electronics and accessories
http://www.taylormadegroup.comThese are the guys that make the glass windshields
http://www.theboaters.comAnother good boating forum
http://www.uspowerboating.comOn-line power boat training
http://www.oceaneastmarine.comClosed cooling systems and re-powering
http://www.wholesalemarine.comTheir name says it all...!
Being on the other side of the world, it is good to find people that can ship to me at a reasonable price.