There are plenty of reef inhabitants, including coral, that can go into a tank after a normal cycle (I'm thinking particularly zoanthids, corallimorphans such as the mushroom corals (Discoma sp, Ricordia etc), leather corals etc), but jmeader is right that some of the more sensitive inhabitants would benefit greatly from a much more mature tank. This is especially true for SPS coral, anemones, mandarin dragonets etc, where 6 months would be the minimum and preferably longer - but these are not ideal inhabitants for a nano anyway (mandarin dragonets are to be avoided in particular with a nano, unless you want to watch your fish waste away). If you stick to easier to keep fish and coral (like the ones I mention above), you don't have to wait 6, or even 3, months.
Of course, there is a perfectly valid school of thought that, if you want as diverse a tank as possible, with as much natural food (pods etc) as possible, then you do exactly what jmeader is suggesting (it's actually what I'm planning to do with my next tank). But this isn't obligatory and, to my mind at least, is a less productive strategy with a small aquarium anyway (I'm planning to do something like this with a 90-100g tank).