Will not shift out of Neutral

I have a 99 Chevy S-10 and today while driving home it would not shift out of neutral at a stop light. What could be causing this issue and what steps should I take to allieviate this problem.

It is a Standard Transmission

I replaced the clutch 2 years ago, so not sure if that is the problem now or not. Anything else to check first before dropping in a new clutch?

Thank you.

4 OR 5 SPEED?
4W drive? Did it go to neutral?
Can you feel shift stick shift the trasnsmission into all gears?

5 speed 4WD

It was put into neutral at a stop light then never came back out. No the gears do not feel like they are going into the transmission at all.

I would pull the shifting stick and see if it is broke or jumped the forks or the plastic ball on the end of it broke.
MT

If the truck is turned off will the trans go into gear? It is possible that you have an issue with the hydraulic clutch system, that is not allowing the clutch to disengauge all the way.