All sorts of random information on Frankfurt from other expats
http://www.toytowngermany.com/frankfurt/

List of Frankfurt based expat bloggers

Travel and transport, accommodation and schools
http://www.expatarrivals.com/germany/frankfurt/moving-to-frankfurt

Partial description of districts
http://www.expatarrivals.com/germany/frankfurt/areas-and-suburbs-in-frankfurt

Cost of living breakdown
http://www.expatistan.com/cost-of-living/frankfurt-am-main

Social and night life in Frankfurt
http://frankfurtsbest.com

Registration required, but some good articles on healthcare and transport
http://www.internations.org/frankfurt-expats/guide/living-in-frankfurt-15849

English-speaking tax advisor
Sina Neumann

English-speaking insurance advisor
Barry King

A great blog if you live in or near Rodelheim, but you may want to switch on Google translate…:
http://www.roedelheim.blogspot.de/

Humorous (and sometimes rude/irreverant) take on life in FFM with the help of animated gifs
http://fuckyeahfrankfurt.tumblr.com/