The datasheet at http://www.sparkfun.com/datasheets/C...nts/LM7805.pdf recommends a .1uf input cap and a .33uf output cap. Even if it's something close to those values you should have a fairly well filtered power supply. You don't say what PIC you're using but the value of a cap connected from power to ground at the chip socket is usually specified in the datasheet. If you'll show a schematic someone else might see something more specific.