On the main page, click on Browse by Topic for a list of the most commonly used tags.
Since your question is about the subjective content of Questions in general, browsing the tags is likely gonna be the best way to go, short of engaging some data mining tools.
@east The likelihood of exact wording being the same is very small, which makes it somewhat subjective what one considers the “same” question. Therefore, I think Rob’s suggestion is excellent.
@beast, it won’t take you long to notice that good spelling is not exactly de rigueur for our iPhone-based Flutherites. So you’d be hard-pressed to get exact matches for that reason alone. (Ironic that the most tagged topic is also likely one of the hardest to match؟)
i think it would be tough to figure it out, because you would have to do a server search or something, but small variations in the wording could make it so that it would not list the questions as the same thing