Who knows a good component for a “calendar control” (NOT date/time picker)?
“Calendar control” means something like Mozilla Sunbird: 
(source: mozilla.org)
Requirements to the control:
– C++;
– Day/Week/Month view;
– Support of several calendars;
– Without MFC dependences;
Nice to have:
– Open source;
– Cross plathform;
– Free;
– Minimum external dependences (boost etc are fine);
You are unlikely to find such a control ready made.
Even more unlikely to find one for C++ without MFC dependencies.
Your best bet is to implement it yourself.