Expanding on the answers by Tobias Kildetoft and Joseph O'Rourke.
There is some kind of automatic Best Of:
- http://mathoverflow.net/?tab=monthhttps://mathoverflow.net/?tab=month (the few on the top are almost always of general interest)
- http://mathoverflow.net/?tab=weekhttps://mathoverflow.net/?tab=week (to be more up-to-date and less selective; still, questions there are usually decent)
Also, based on comments there are some StackApps, for example:
For more manual choice of questions (in the spirit of Editor's Choice or rather... Mod's Choice), I think the simplest way is to share links on G+ or Twitter (especially as sharing is already built-in).