Let $G$ be a connected, simplyconnected complex semisimple group. We have the famous Springer resolution $$T^*(G/B)\rightarrow\mathcal{N}$$ of the closure of the regular nilpotent orbit. My understanding is that the closures of nilpotent $G$orbits $\mathcal{O}$ admit symplectic resolutions $$T^*(G/P)\rightarrow\overline{\mathcal{O}}$$ when $G=SL_n(\mathbb{C})$, but that this need not be the case for other $G$. Accordingly, I am looking for a reference giving some information as to which nilpotent orbits have their closures resolved in this way.
This is answered (except for a few cases in $E_7$ and $E_8$) in: Baohua Fu, Symplectic Resolutions for Nilpotent Orbits. Maybe it's worth mentioning: orbits which are the image of $T^*(G/P)$ for some $P$ are called Richardson and are relatively easy to understand. The tricky part is know when that map is a resolution, since in many cases (outside type A) it is finite to 1 instead. One useful criterion is that it will be a resolution it the orbit is simply connected. 

