Creating a slice from a selection
It would be incredibly useful and handy if, once we rectangle-select something, we could hit a hotkey to make it a slice, without having to laboriously zoom in on each of the 4 edges of the object to slice to make sure the slice is cut sharp around the object.
Does it exist, and if not is there a plugin that does it?
One good option:
If your desired object is on its own layer (which is often is, if you've built the layout yourself in PS), you can use the Layer > New Layer Based Slice function, then Save for Web. In the first subsequent dialog box, choose your file format and settings. In the second dialog box, select "Selected Slices" from the bottom drop down menu:
Hit "Save", and repeat as necessary.