Pick an open source community and you will find plenty of help.

Paid internships with assigned mentors are also available through Summer of Code, Outreachy or project specific programs:

https://developers.google.com/open-source/gsoc/ http://www.outreachy.org/ http://www.x.org/wiki/XorgEVoC/

OpenHatch is a great resource too:

https://openhatch.org/