For some reason I have to draw a lot of venn diagrams and I hope I can just specify the sets
and its elements
and it emits the right image. I do not care about the blazonry.
So is there any tool or script or libraries suitable?

pyVenn is a python library that shoud help you: http://code.google.com/p/pyvenn/ an alternative would be matplotlibvenn, which the author describes here. It supports multiple sets, but depends on matplotlib. 


Venn Diagram Maker by Creately:
http://creately.com/DrawVennDiagramsOnline Grapholite allows you to easier create a Venn charts by offering the following abilities:
http://grapholite.com/Diagrams/VennDiagrams Gliffy’s Venn diagrams: Use one of the preprepared Venn diagram templates, or create your own using the extensive library of shapes and images. Draw, style, and align shapes and easily insert and format text using marketleading Venn diagram software. And because Gliffy is collaborative online software, it’s easy to share the Venn diagrams you’ve created by inviting other users to Gliffy, exporting them as images or PDFs, or embedding them in your blogs and wikis. 


Excel includes this functionality. Microsoft's documentation for creating Venn diagrams is found here: http://office.microsoft.com/enus/excelhelp/createavenndiagramHA010335959.aspx 


There are a few relevant options: Lucidchart has a Venn diagram maker. It provides a lot of flexibility but the tradeoff there is that it requires a bit more manual effort to get it sorted correctly. matplotlibvenn is a Python package that is more scripted. 


I use the venn diagram template from Lucidchart to draw mine. It is super easy to use and integrates with google drive. 


This one is good for generating 2 or 3 sets, from real data http://simbioinf.com/mcbc/applications/genevenn/genevenn.htm 

