Well, my tallest pair would be my Cole Haan Tivona Air Sling with the Nike Air Technology (which I still need to review...I didn't forget!). They stand with a 4" heel and are my tallest pair by 1/2 an inch. Click to see details
Anywho, since I've already posted that pair before, here are my next tallest - these have 3 1/2" heels:
From left to right: Black patent slingbacks by BCBGirls, Silver Espadrilles by bebe, Blue Pumps by MICHAEL Michael Kors (you've prolly seen this MK pair a couple times...I love them!)
Too bad I couldn't afford those Louboutins I was lusting over last season...then they'd be my tallest!