Some of Apple's patents, I am pretty sure are based on Prior art some of these include:

Patent US 7844915. Here is its claim 1:

A machine implemented method for scrolling on a touch-sensitive display of a device comprising:

• receiving a user input, the user input is one or more input points applied to the touch-sensitive display that is integrated with the device;
• creating an event object in response to the user input;
• determining whether the event object invokes a scroll or gesture operation by distinguishing between a single input point applied to the touch-sensitive display that is interpreted as the scroll operation and two or more input points applied to the touch-sensitive display that are interpreted as the gesture operation;
• issuing at least one scroll or gesture call based on invoking the scroll or gesture operation;
• responding to at least one scroll call, if issued, by scrolling a window having a view associated with the event object based on an amount of a scroll with the scroll stopped at a predetermined position in relation to the user input;
• and responding to at least one gesture call, if issued, by scaling the view associated with the event object based on receiving the two or more input points in the form of the user input.

Patent US7864163. Here is its claim 1:

A computer-implemented method, comprising:

• at a portable electronic device with a touch screen display;
• displaying at least a portion of a web page on the touch screen display, wherein the web page comprises a plurality of boxes of content;
• detecting a first finger tap gesture at a location on the displayed portion of the web page;
• determining a first box in the plurality of boxes at the location of the first finger tap gesture;
• and enlarging and translating the web page so as to substantially center the first box on the touch screen display, wherein enlarging comprises expanding the first box so that the width of the first box is substantially the same as the width of the touch screen display;
• resizing text in the enlarged first box to meet or exceed a predetermined minimum text size on the touch screen display;
• while the first box is enlarged, detecting a second finger tap gesture on a second box other than the first box;
• and in response to detecting the second finger tap gesture, translating the web page so as to substantially center the second box on the touch screen display.

The first includes gestures like pinch-to-zoom which have been in use long before Apple's patent was filed. I believe the first implementation of a pinch gesture on a touch sensitive screen was in the late 1980s, if this is the case it could invalidate the patents as Apple were not the inventors of the technology.

The second is based around a tap-to-zoom technology, which means taping a portion of a screen to zoom in or out again this has been in use long before Apple filed this patent in my opinion.

There are in my opinion many other patents filed by Apple based on prior art, but these are the ones I have found so far.