isopropyl alcohol (nail varnish remover), alcohol-ethanol, meths, paintbrush cleaners (although these leave a nasty smell when you put the chip back in cause they arent pure solvent the "extra" cleaning stuff in it gets burnt off - but that's also brand dependent obviously). Generally any organic solvent should do it.
I used alchohal and some toilet paper to get it off the heatsink/fan. Used a fingernail after putting some alchohol on the stuff to get it off the CPU. Works like a charm.