We really liked the Henge Gravitas iPhone/iPad Dock in our May review but lamented the fact that it wouldn't work if you used a case for your iPhone. Henge has released an iPhone case compatible insert that sells for $9. They've also dropped the price on the dock itself and now the Lightning connector version sells for $69 and the 30-pin version goes for $49.
That's obviously not cheap but this is a beautifully made product and it's a much better value with the $20 price drop.
Henge has put together a list (click the far right tab at the linked page) of both compatible and incompatible cases so you have a good idea if your preferred case works with the insert. If your case isn't open at the bottom, it's not going to work, which rules out the hardcore protective cases like the Trident, Pelican or Otterbox.
Still there are a lot of lightweight cases that work. The new insert and the new price make this a much better value.