Work you can help out with:
PTs and rate limiting (https://lists.torproject.org/pipermail/tor-dev/2013-September/005419.html)
Write collection of Unix one-tool-per-task transports. One transport that simply obfuscates data. Another transport that simply changes data length. Another transport that passes transport through XMPP. Then pipe them together in layers to get combinations.
And here are some coding tasks in case you want to write some code:
Tor tickets (in C):
obfsproxy tickets (in Python):