Once we design a web project in Photoshop, it takes some time to slice it and export all the assets to multiple image files.
Cut&Slice me is a great and free Photoshop plugin that can fasten this process with the smart features it offers.
First of all, it trims any unnecessary pixels while exporting. Also, it understands that "a group of layers" needs to be treated as a single object and cuts them perfectly.
When designing buttons, once the layers are named with the format mentioned by the plugin, it can auto-slice the multiple states of that button.
Also, for designs created at full resolution, Cut&Slice me can export to iPhone + Android retina/xhdpi (ldpi, mdpi and hdpi) with only one click.