Excluding Cocoa (and its NSThread), what multithreading libraries would you recommend?
The application's engine must run on multiple platforms (Windows, Linux, MacOS, iPhone), and be multithreaded. Abstracting the library to compile against platform-specific MT libraries is possible, but incurs an extra layer of overhead and complexity.
How about something in the C library area? e.g libapr: http://apr.apache.org/docs/apr/1.3/group%5F%5Fapr%5F%5Fos%5F%5Fthread.html
or glib? http://library.gnome.org/devel/glib/stable/glib-Threads.html
Regards
NSOperation works fine. As an added bonus you get a thread pool for free, and can setup a dependency chain between operations.
I would start with Grand Central which was recently open-sourced: http://libdispatch.macosforge.org/