As venerable as 'tail -f log/development.log' is to a Rails developer (and as undeniably useful as well), I've been using another tool that has been tremendously helpful in weeding through all the noise. Spike, written by Matt Mower with help from the Rails community, parses your development log and presents, in two windows, summary information and a detailed view.
Spike lets me see the flow of the application by filtering out records that aren't pertinent to what I'm looking for. For example, the 5 second refresh event coming in from EVERY browser -- ZAP and they're gone! I can filter by request, IP, session ID and so on. The detail viewer shows me all the parameters, the renders and all the activity in the log that is part of the request.
This has been a very helpful tool; my thanks to Matt and everyone who worked on Spike!