I use an automatic so I don't really know what it could be... but I did do a little research and found this, maybe it will help? Better than no answer at all I suppose..
"Although the squeak is annoying, unless it is loud or grinding it is usually harmless. However, if you want to get rid of it, there are two areas pf the clutch system that you need to look at: the master components and the slave components.
First, try to determine if the problem is in the clutch pedal and linkages (master) or in the clutch fork linkages (slave). Have a friend move the clutch pedal while you get your ear (or mechanic's stethescope) down where the squeak is happening. Once you do that, do one (or both) of the following:
Lubricate master components (inside the car). Get a can of lithium grease with the nozzle tube that will allow you to get into the small spaces. Pushing the clutch pedal with your hand, thoroughly lubricate all points of contact. Note: if this does not resolve the inside squeak, disassemble, clean, and lubricate the clutch pedal and linkages. Commonly, the squeak will be the clutch pedal pivot point, or the master cylinder shaft contact point.
Lubricate slave components: This is the most common cause for the squeak. Crawl under the car and peel back the boot covering the slave cylinder/clutch fork. Clean this area well, being careful to not get anything on the flywheel. Apply a high temperature grease to all contact areas, especially where the slave shaft pushes against the clutch fork. If you cannot access this by peeling back the rubber boot, you will need to unbolt (carefully) the slave cylinder from the bell housing and perform the above steps."