Can I Plant Herbs in August?

I purchased a fair amount of herbs from Richters this spring, and am pleased with the results. Never before have I been overwhelmed with the desire to plant a couple more things NOW... If I water well, get them off to a flying start, then mulch aggressively for winter, do they have a chance? I live in zone 5.

Absolutely. We plant hardy herbs right up until the end of September. We are in zone 5 also.
As is the case with many herbs, good drainage is as important as the mulch. If you soil is a heavy clay soil you need to add sand to improve water drainage. Planting on slightly higher areas where water can run away from the plants helps keep the water away from the roots during the freezing and thawing cycles that occur during the winter months.