You need to wedge an Arduino into a really tiny spot? Simple - just use a SMD '328 IC. Oh... you want a reset, and voltage regulator too? Why didn't you say so!
You want Arduino-to-the-max? With a great variety of add-ons? This is the official made-by-Arduino super-development kit, all plug-and-play! Can-we-add-more-hyphens? Let's try!