What a place! I still remember saying to pilot "I have acrophobia (fear of heights) and I'm doing this (paragliding) to overcome that fear. A place full of adventures such as paragliding, river rafting, hot air ballooning, rope river crossing, and many more. Though, summer is the best time to visit hill stations but from my experience I would suggest not to visit during may because you will need to tolerate heavy traffic (It took me around 6 hrs to travel 8 km). If you ask me the best food I ate in Manali, then my answer will be "kashmiri Aloo-Dum". It's been more than a year since I visited Manali but I still crave for that dish. Potato stuffed with paneer and coconut mixture, makes it so delicious.
Don't forget to visit Rohtang Pass (52 km from Manali), it is where you will find most of the adventures, though you can do paragliding at Solang valley in Manali. You can take rented bikes to ride on your own or can rent a car. I would suggest to rent a bike to escape the road quickly and to have some amazing experience, driving in the hilly roads.