If you avoid web programming and SQL-heavy enterprise development C++ is very much mainstream and wouldn't call it a specialist need. Actually, the kind of open source projects I enjoy to tinker with [when not at work] is all C/C++: Qt, Webkit, SQLite, various compilers and interpreters, search engines, etc.
SQLite is written in C.
Excellent taste in tinkering, but ... ahem ... aren't those a tad on the infrastructure side ? ("Is this the right room for an argument ?", or are you setting a subtle trap ? ;-)
I don't doubt that most of the (non-idle, non-phone/TV/etc.) CPU cycles in the world are probably being burned by executing code written in C/C++. But the stuff in my shopping bag probably also did better than 90% of its movement by truck/train/ship.
P.S. Mark Dufour's ShedSkin may have you covered for 100x of that 200x speed hit you mentioned in another thread: http://www.hxa.name/minilight/#comparison is instructive (one small case, restricted, etc. Void where prohibited by law).
Speaking of Python and C++: possibly some of us would wish to write Python and get C++. Mark Dufour has been persistently plugging away at a Python-to-C++ compiler (and welcomes help): http://shed-skin.blogspot.com/