Hashtags for Strava Activities and easy categorization/search
It is really frustrating trying to comb through a plethora of rides to find one particular ride that I would like to re-do, or maybe integrate into a new route to plan. Or even just looking up previous rides that I remember as being fairly hard/fast/easy and wanting to recheck the data from it. "When was that again? Uhhh...sometime in the fall." The training log makes it a bit easier, but still doesn't get the job done as streamlined as it could.
If users could add hashtags or otherwise tag their rides (besides 'Commute' and 'Stationary Trainer'), it would be easy for users to search their own tags for rides with certain clubs, races, or even characteristics about the ride (specific hills, rest stops, etc.). That way, assuming that I tag the rides as I do them, it would be pretty easy to find them again by searching my own tags. No more manual searching.
The tagging system could work site-wide (adding to a pool of rides by all Strava users), but it might be easier on the servers, and a bit more private, to have the tags function only within each user's history of rides.