I bounce around a handful of aerial map sources and have found that you need to pay attention to when the picture was taken for your specific area...

I subscribed to www.mapcard.com for $20 / year.
It allows me to make detailed maps with different markings/trails and GPS coordinates, etc, then save them to my computer as a jpg for future usage, etc...
The downside of map card is my areas aerial photo was taken in 2005.

However, I jump to another site and then pencil in the changes from another site that has 2007 photos, if I plan to scout, etc.
Of course a drive bye will confirm my findings from the photo and more.