My 2005 Pontiac Sunfire intermittantly grinds when shifting into first gear. This has been happening ever since I took the car in for its 60,000 mile tune-up early this year. I replaced my clutch three weeks ago but still have the same grinding every so often when shifting to first at the stop light and/or parallel parking or pulling out of my parking spot in the morning. Any ideas as to what the issue is?

I would say that it should be related to the clutch pedal. It isn't releasing the clutch completely.
If you find that the pedal is fine then either the the clutch asm. is defective or there is a problem with the synchro, for first gear.

I believe the problem is the first gear synchronizer. They are what allows the gears to mesh together without grinding. As they wear, they are less able to mesh the gears together without grinding. The first gear gets used the most, so that one usually wears first. Each gear has them, so as time goes on, the others will wear. To replace the synchronizer/s, involves diaasembling the transmission. I would have the transaxle fluid level checked, maybe as simple as that. But usually it's the prior.