What is the minimum ceiling and visibility limits in Class E airspace?
VFR cloud clearance requirements are listed in 14 CFR 91.155 and for Class E airspace specifies:


  Class E:
  Less than 10,000 feet MSL.
  Flight Visibility: 3 statute miles
  Distance From Clouds: 500 feet below, 1,000 feet above, 2,000 feet
  horizontal.     
  
  At or above 10,000 feet MSL.
  Flight Visibility: 5 statute miles
  Distance From Clouds: 1,000 feet below, 1,000 feet above, 1 statute
  mile horizontal.


There is also a requirement specific to Class E surface areas that says that the ceiling must be at least 1,000 feet in order to operate in the airspace.  It is also listed in 91.155:


  (c) Except as provided in Sec. 91.157, no person may operate an
  aircraft beneath the ceiling under VFR within the lateral boundaries
  of controlled airspace designated to the surface for an airport when
  the ceiling is less than 1,000 feet.


Note that there are exceptions for both of these that refer to 91.157 Special VFR Weather Minimums if you are instrument rated and the aircraft is instrument equipped.