I was thinking of building a C# UDP listener to connect a log4net UDP appender to. Something like this - Code Project: A log4net Realtime Color Console for ASP.NET
The trick would be getting a setup that would work for multiple developers. A service that accepts the UDP packets and relays them out to registered listeners or something such similar.
After some quick Googling I found it would be quicker to have each developer just point a log monitoring tool at the output from a RollingFileAppender. BareTail seems to do a pretty good job.
Updated: When combined with a RollingFileAppender using XmlLayout Log4view works well to filter out the loggers.