Today, I read the following paper: 

This one is really just about a fairly simple method to assay protein-protein interactions. It's an advertisement: the method was developed commercially by ChromoTek Gmbh and is sold as a kit. The basic idea is that proteins are expressed in Baby Hamster Kidney* cells as GFP and RFP fusions. The GFP-fusion baits also have LacI, so they'll end up bound to lac in the nucleus no matter what happens. The RFP-fusion preys should just float around the cell unless they interact with the baits, at which point they'll also be present at the same spot as the GFP. The process is reversible, so an interaction can be observed in real-time as it is disrupted, i.e. by some variety of specific protein binding inhibitor.

I probably won't use this method much myself, but it's quite simple and looks like it could be convenient for screening potentially therapeutic small molecules or peptides. It would be nice to see a paper published about the method's applications by groups other than ChromoTek employees.

*There's something about the word "baby" that makes it difficult to take seriously. This is an established cell line and has been in use since the 60's.