If you want to do a project using PIC controllers, then take the advantage of its RISC architecture (high speed). There are many things that could be done....like you can take data from different sources like PC, telephone line etc in to the PIC controller and then convert that data into PCM frames (64 kbps) or ADPCM form (32 kbps)....i will suggest you to search different university web-sites for projects.
You can try some measurement instrument based on pic, like an oscilloscope or logic analyzer, besides if you have skills in computer languages you can take advantage on making the user interface to display the procesed signal.