How about a "Sticky Forum" for everything that needs to (or could) be a permanent thread for a reference for everyone? In addition to this thread, Ted Hikel's threads on different types of rolling stock would be another example of one that could go there and there are more, just can't think of any right now.
It could be like a FAQ for ideas on toy trains and model railroading forum or something. There are a lot of things that come up very often like which track planning software to use, how to wire LED's, DCS and Legacy how to questions, etc. I think there is a scenery source list and other things.
I have seen many threads like this one that I would like to refer back to occasionally, but find it difficult to keep track of the many different threads. I'm sure not all of anyone's desired threads would be kept there, as we all have different ideas of what to keep, but it would be a good starting point.