I enjoy historical museums and reading local history. I have a special fondness for Haarlem.
I keep a total list of artists referenced in Arnold Houbraken's "Schouburgh" (3 volumes, published in 1718, 1719, and 1721) here, and a rough measure of progress is here.
I also try to keep the interwiki links up to date between the Engish Wikipedia and Commons for these artists. Now and then I update this list as I untangle more artist names (Houbraken's spelling and use of nicknames can be very confusing). In my opinion this entire book could be indexed on Wiki source, and I have already started to do this, but I could use some help.
The interesting thing about this project is that it is a project without borders, since paintings and associated engravings by these artists are spread today all over the world. As such it has helped me learn about the power of wikipedia collaboration.