What's worked for you in the past, stability-wise? Most shoe companies today make both street runners and trail runners, so if one brand has seemed to handle your pronation problems well (a problem I share) then go for that brand's trail runner. For instance, I always thought that shoes from Asics handled over-pronation very well without resorting to too many in-shoe gimmicks. In a trail runner, you might look at the Gel-Trabuco V ($80; www.asics.com), a shoe designed for high stability. Asics just came out with the Trabuco VI, the same price but I think just different graphics.
New Balance also makes some very stable shoes. For trails, check out the New Balance 806 ($85; www.newbalance.com), which has an external heel counter to hold your feet in place. And there's Montrail's Diez Vista ($95; www.montrail.com), a shoe designed for the runner who needs extra foot stability.
It's also possible to purchase a trail runner for its fit and cushioning, then to add stability with an after-market insole. The Superfeet Active Footbed II ($30; www.rei.com) is the choice here.
So, hope that helps. Happy running!