One type of IP blocks I have a lot of experience with comes from ARM Ltd. themselves and those are called "PrimeCells". Those are given in source code (VHDL) form to vendors licensing ARM CPUs, more or less as "no strings attached examples". Numerous vendors have since modified the silicon in several ways, fixing hardware bugs etc. But all in all, they could mostly all use the same driver, even though things have been extended and moved around.
It would actually have been a good thing if the VHDL for the IP blocks were Open Source, because many vendors seem to be fixing the same bugs in hardware too. But the world seems not to be ready for OpenCores just yet. :-(