oh we've covered this before
but because i cant for the life of me remember what the thread title would be, and because it happens to me too ill post what i do:
soft-solid deodorant like "secret conditioning solid". it works miracles. i use it when i play soccer, or wear tights for work, or any activity where i know my thighs will sweat/rub and get uncomfortable.
because its creamy its easy to apply in places like, um, not crotch? areas, but right near there. you can get unscented if you are worried about, um, reactions, near that sensitive place