This afternoon while preparing to brew I cracked the Wyeast pack and the package broke all over the kitchen. The bag still has some liquid in it. I am wondering if I should continue with my brew tonight and pitch the remaining yest or hold off till tomorrow and get a new package of Wyeast and brew then?
I'd go with a new pack. You have no way of knowing how many yeast cells you're starting with now, not to mention the contamination issues. It's worth $8 to eliminate a chance of ruining a whole batch of beer.
If your sanitation was good, I think it's certainly better than pitching a fraction of a bag of potentially-contaminated yeast. Let us know how this brew goes, but I'd vote for sealing it up tight and pitching new yeast tomorrow. Under pitching would not give good results.