Well, I've registered on this forum after I saw this topic. Ok, no more offtop...
Firstly. Mounted crossbowmen? Not in Poland, really. By the way, you should look for knight brotherhoods in Poland from XIII century - there is really much of them!
http://www.bagrit.pl/bractwa/bractwa.php?lg=en - here you can find almost every brotherhood from Poland. Simply tick XIII century
http://gorg.i365.pl/galeria/ - gallery from much partys et cetera from XIII century. Really, it's good for it!
Other. Javelins? Never.
Normal knight with horse had shield almond (tear?), full chainmail, great helmet, mostly lance and one handed or hand-and-a-half sword (second only if he was really strong, because mostly they weren't able to use both shield and hand-and-a-half). His horse wasn't armored, no chainmail et cetera; only sometimes he had armored head. Mostly anyway he had his rider's heraldic sign on himself.
Ah, and as somebody up from me said - there wasn't Poland. There were much 'mini-countries', like Mazowsze.
EDIT:
There weren't archers on horses, not really, it was very rarely seen in any countries army. Like half of army it was medium cavalry. Don't forget about soldiers on-foot, anyway; we hadn't or had very small amount of crossbowmen!
I am sorry for my big mistake! Just a second ago I saw an old image on which anybody can see crossbowmen shooting from castle. They were in light armour - chain helmet and gambeson (Papierek, thanks for translation, I really wasn't able to find that in Uncles' Google ;-) ). But still - no mounted crossbowmen!