Please recommend open source project to get involved in

Please recommend open source project to get involved in

I want to improve my programming skill and build my technology database.
Reading good quality codes of some open source project and get involved in
developing are the best methods. However, there are too many projects that
I have no idea which ones should I focus on.
So I list my objectives below, please recommend your best experienced
projects that cover these items. The more the better. Thanks in advance!
1: Database(Oracle, PostgreSql)
2: Linux kernel(Memory management, File system, IPC, device driver)
3: Networking, socket programming
4: Multi-threading/processing, parallel computing
5: large scale data mining/learning
6: Language: Java/C++/Python/
7: New c++ library such as LR1, LR2 or BOOST.
Appreciate!!