If you want to contribute (implement something from the current list, or
anything), contact the developer's mailing list (gnutls-dev@lists.gnupg.org),
in order to avoid having people working on the same thing. 

Current list:
+ Add ability to read PKCS-12 structures (certificate and private key)
+ Add support for temporary RSA keys (needed in EXPORT ciphersuites)
* Add function to return cipher suite names
* Convert documentation to texinfo format
* Merge common stuff in DHE and DHA key exchange
* Add GPGSM certificate manager support
* Add support for certificate CRLs
* Audit the code
- Add Kerberos support

(+) Means high priority 
(*) Means medium priority
(-) Means low priority (ie. nobody is interested to develop that)