I asked a question a while ago to figure out how to split a line layer with a points layer using QGIS, but cannot, however, get the accepted answer to work due to limitations of my knowledge and the fact that i'm working on Windows 7. I noticed this feature request that dates from about a year ago, requesting a tool that accomplishes exactly what I need. I've been looking for it, don't see it, and am wondering if it is currently an available tool and i'm just not looking in the right spot or not.
The Networks plugin has a function called "Connect":
This tool allows you to connect node layer objects to a linear objects layer. Each point will be connected to the nearest polyline, if the shortest distance to the polyline is lower than the search radius, the polyline will be split in two parts from each side of the connection point, in order to preserve the network topology. NB : Multilinestrings are ignored