Unoffical sites:
Instagram and Tumblr have multiple Prince themed accounts as does Pinterest. You can check mine out HERE.
Sometimes dicey ‘fan’ site with discussions on Prince and associated artists
Information on every Prince show, recording, performance and release; kind of a Princeapedia
For merchandise: ElectricFetus (Minneapolis record store)
Fabulous variety of Prince pins available HERE.
Links to great Prince interviews on the next page, including the famous one with Sherri Shepherd when he surprised the ladies of The View.