App Grid is a lightweight software center which is being considered as an alternative to Ubuntu software center, it’s been a quite while when the first was released, written from scratch, delivers stunning startup speed, and swift reactions throughout, and now it is matured enough.
It is equivalent to Ubuntu software center, but works slightly different. App Grid uses same sources which are already added to the system and shows application/updates. There are options to filter applications by categories, installed/pending, name or by top rated.