For starters, look through the BOINCzilla bug database and try fixing a bug or two. Sign up for the boinc_dev email list to communicate with other BOINC developers. Also, read:

• Get and compile BOINC software
• BOINC coding style

• BOINC Manager: Change the Statistics tab to use a single graph with different colors for different projects.
• BOINC Manager: Use progress bars for file transfers and in-progress results.
• BOINC Manager: Use pie charts for disk usage
• Disk space management: prevent disk space usage from exceeding user preferences, and enforce resource shares, with file deletion according to project policy.
• Use database IDs instead of names to identify results and WUs in the core client (to increase efficiency in the server, since indices on integers are apparently more efficient than indices on text fields). This involves minor but pervasive changes.

Core client

• File structure
• FSM structure
• Data structures
• Main loop logic
• Client scheduling policies (new)
• Client scheduling policies (old)
• Debugging
• Host measurements
• Host identification
• Core client/application interaction (basic)
• Core client/application interaction (graphics)

Server programs

• The BOINC database
• Work distribution policy
• Backend state transitions
• The logic of backend programs
• Debugging server components

Protocols

• Protocol overview
• The scheduling server protocol
• Scheduling server timing and retry policies
• Data server protocol
• Persistent file transfers

Miscellaneous

• Python framework
• Preferences
• Trickle messages
• How to see what has changed between two versions of an executable.
• Account management systems
• Spec info for RPMs
• Statistics summaries