My goto place on twitter (Which always makes a great starting point for finding other related twitter streams)
http://twitter.com/picsofsexiness/
From there I have some custom software I've written myself in C# that I can just feed account names into and it goes back as far as it's able too and downloads any pictures it finds.
Once pics on my HDD it's just a simple matter of sifting through them at my leisure.
I'm currently on writing a C# application that will go through a folder of images and give a "Flesh Score" that is what % of the image it thinks is naked flesh, then produces a report telling me which images are the most likely to have nudity in.
Not finished it yet though, and tbh don't know when I'll get time to either considering the amount of paid for software jobs I have to write at the moment :-)