Cool so lets start off with some forum and site links.

• MultiRotorForums
• FPVLAB
• Flite Test These guys while not strictly rotors are fantastic, do custom builds and walk you through the process. If you don't look at any other links here at least check them out.
• RCGroups
• Important parts and cost of DIY racing quadcopter project Albeit a bit expensive for an initial build it will at least give a good idea of what DIY Racer build may look like.
• 250 Racing Quad Frames I swear I am not plugging this site and have no connection to this sight whatsoever, but this is a pretty solid breakdown of the 250 frame.

To be continued, will add more later and if yall see any that you would like up then comment away.

Now for some hobby sites, I do not receive anything from any of these sites or have any affiliation. Just a couple I've come across over the years

• MultiRotorUSA
• Hobbytron
• Amazon For those of you who are lazy I linked their UAV section but really you can search the whole website, I was seeing a bunch show up under "Adult Toys"...Haha
• FoxTechFPV
• MultiCopterWarehouse

Now this list is by no means all inclusive, a solid google search will net you a ton of results and if some of these sights seem primarily USA oriented I apologize my brethren from overseas.