we are developing an offline city map application for iPad, using Cloudmade SDKs. I\'m curious, is there are any other SDKs which could be used for offline applications ?
Starting with April, 2014 there is also skobbler's /Telenav's SDK - it's got full offline capabilities (map rendering, routing & rerouting) and a map cutting tool if you want a map of a custom area (e.g. you provide the gpx enclosed polygon and you get back a map of that area)
See some examples in the demo apps and the how-to's