Please help me identifying these spaceship parts - big sloping ring
It's from a LEGO UFO set from the late 1990s. You can see all the sets in this theme here: http://www.bricklink.com/catalogList.asp?catType=S&amp;catString=34.311. What you have is most likely the #6975 Alien Avenger:  http://www.bricklink.com/catalogItem.asp?S=6975-1