From the search results I was able to get so far my question seems unlikely, although I don't know why ;-)
I'm writing an installation guide for a program and need a “compatibility matrix” for several packages on the different distributions. So what I need is the information in which distributions and releases a given package X is available, optionally together with the version.
Of course each distribution has a package index like Debian Packages Search from where I can get the information for this distribution. But is there an index or a search engine anywhere that can give me this information for many (all?) distributions?