The online Image Gallery and Special Collections of Dublin's City Libraries continue to grow at a pace and are definitely worth losing yourself in for a few hours.
The Special Collections portfolio is also great fun to rummage through. My favourites include the tram timetables, old maps (I confess to being a map-nerd) and a 1736 newspaper advert for a tincture that 'immediately expels wind from the stomach' and sorts out your belchings and hyck-ups. Useful stuff!
All online at www.dublincitypubliclibraries.com.