One of the greatest threats I can see to the anonymity of the Tor network and its users, is NSA/GCHQ (etc.)-operated Tor nodes.
No matter how state-of-the-art 'good practice' a Tor user adheres to - in not mixing modes of anonymity, keeping fingerprinting and trackability to a minimum, and using encryption to a maximum - if the NSA has enough nodes under their belt, then they can (some of the time), piece together the dots of the anonymity network and de-anonymize communications taking place in it.
The obvious best thing to fight such NSA compromise of the Tor network, is to use 'people power' (there are more of us than in the NSA), to create as many of our own non-NSA relays (even if on small pipes and not always having 24/7 up-time), and hold as much of our own stake in the network, as possible.
What can one do apart from already hosting a relay yourself?
Is there a foundation to which one can donate (or even partner on charity events) which then sets up Tor community-controlled nodes to expand the network outside of NS control?
What activism, evangelism, or community-building could one do, or join?
(This would be activism/evangelism specifically for more non-NSA nodes being hosted mind you, not so much more Tor users, even though that would be of great benefit to Tor anonimity and potentially indirect benefit to more relays being set up anyway.)
Further to this, is there some big decision that the Tor Project could make that automatically increases the amount of community-hosted relays (thus everyone outside of NSA's anonymity) - such as making all Tor users contribute a bit of (p2p-style) middle node bandwidth to the network whenever they're connected, which might be in such a way that the user's browsing isn't even slowed down?
Perhaps this final idea is one of the best we could do to truly combat NSA Tor network takeover: a vast increase in Tor Browser instances of end users hosting the middle node infrastructure, where there's by virtue of the size of the very Tor user base, more control of it by the community, than by malicious sniffing adversaries such as the NSA.