Consult. If you're valuable to your employer they'll want to keep you on-- esp since you know the understaffed teams so well and can fit in seamlessly (read: they don't have to train someone else). You should be able to charge more (50-100%) to cover health insurance et al. and will have more control over your schedule.

I don't know your industry though so it would behoove you to make friends with someone else who consults for your company and figure out what arrangement they have. If the company has done it once they'll do it again.