Generally, I think the Bicycles.SE community frowns on product recommendations and we close a lot of questions of the sort.
However, there is a decent number of questions such as "I would like a bike for commuting, is this one good"?
I was thinking of something similar to the big-list tag on Math.SE for two common questions we have, which we can point to instead of just closing the question.
The first would be "What should I look for when buying a bicycle?". The answers would be community wikis dependent on the intended use of a bicycle - General advice which holds over all classes (e.g. the fit is important), commuter (e.g. if its wet weather, you probably want fenders), touring (e.g. you don't want that spiffy new road racer), downhill MTB, etc. and feature general things to look for when buying a bike of this type, as well as a description of bikes which fall in this region. By sending people to this question, we can give them useful advice (which holds over time), rather than just closing questions on particular bike recommendations. PeteH had a similar idea with a flowchart (in chat) but I think that would be too complicated to maintain.
The second would be drive train compatibility: "Which drivetrain components are compatibile with which others?". Community answers would be "General advice", "Shimano - Road", "Shimano - Mountain", "SRAM - Road", "SRAM - Mountain", "Campy", and people can add for other drivetrains like Suntour and what not.
Eventually, I'd like to aggregate at least the "What should I look for when buying a bicycle?" question (which is useful for buying new or used) into a blog post on the Bicycles.SE blog if it builds up a decent number and quality of answers.