Was there last weekend, stunning place.
We didn't do too much beyond the obvious (Charles Bridge, Old town, castle, Lennon wall, Dancing house etc) but its a beautiful place to wander around and take it all in. We stayed in a lovely hotel at the base of Charles Bridge on the castle side, in a little area called Mala Strana. It's much quieter than the old town area yet has quaint little streets that are great to walk around, and some nice bars and restaurants dotted in the area too (plenty of baroque buildings, some of which are embassy's), well worth a look if you fancy a change of pace away from the conveyor belt of tourists!