For example, when you search for [google maps flash html5 api v4], Google also shows results for searches like: [google maps flash html5 api], [google maps html5 api v4], [google maps flash api], [google flash map api]. It's interesting to notice that the first page of results shows 2 results for your query and 8 results for related queries, but the numbers are different depending on the query.
Here's another example: [gingerbread install chrome browser manually]. This time, Google returns 4 results for your query and 6 results for related queries. Obviously, you can't install Chrome in Android 2.3 and Google's results should help you find this information.
This feature used to be an experiment, but now it should be publicly available. Unfortunately, Google shows results for too many different queries and not all of them are useful. Some of Google's suggestions remove important keywords from the query and that's a mistake. For example, removing "gingerbread" from [gingerbread install chrome browser manually] returns results related to the desktop Chrome. Maybe Google could automatically detect nonessential keywords and show results that don't include them instead of cluttering the list of results with so many options.