Here is a brief list of things that still need to be done.

More unit tests:
   - Create a MockNetworkConnection and use it to test the Peer.

API:
   - Reorganize the package layout to be more modular.
   - Support multiple active wallets.
   - Allow sorting of transactions by time.

Protocol:
   - Start up faster
      - Store a block locator in the persisted chain
      - Use the getheaders command to speed up the initial chain download
   - Implement tx fees.
   - Longer term potentially add a getmerklebranch protocol command so we can check 0-confirmation transactions.
   - Support PeerGroups for holding open/using multiple connections at once.

Examples/documentation:
   - Implement a simple Swing GUI payment app.

Cleanup:
   - Find a way to avoid some horrid hacks when shutting down the network connection.
   - Implement a BitCoin class that encapsulates a BigInteger and formatting.
   - Make NetworkParameters use subclasses instead of static methods to construct.