I'm using linear regression in Prism to determine pA2 values for a Schild analysis. Can I get the standard error for the X intercept?

See Chapter 43 of FIting Models to BIological Data Using Linear and Nonlinear Regression for an in-depth look at how to analyze Schild experiments. The best approach is global nonlinear regression, not to do linear regression on a Schild Plot.

If you really want to use the linear regression approach, see QA#230.