a library that I plan to submit to boost causes > 50 s compile times even for simple examples, so do you have any recommendations on where to start?
There is a template profiler from Steven Watanabe, you could start there: http://www.boost-consulting.com/vault/index.php?action=downloadfile&filename=profile_templates.zip&directory=Tools&
my library invokes a lot of Boost.Serialization and some MPL/fusion code, so I'm not even sure if I can do anything about that within my library.
As you use some MPL, you should check all your algorithms for complexity (especially if you use many mpl::fold). A quadratic complexity in a metaprogram will hurt you pretty fast. I had the feeling that SFINAE also hurts you quite much on some compilers. HTH, Christophe