Not the usual technical post, but I keep forgetting the process for image stacking in Photoshop CS5

1. File -> Automate -> Photomerge
2. “Browse” for files to be stacked (select files)
3. “Untick” all options
4. Click “OK”
5. Select all the layers to be stacked
6. Edit -> Autoblend Layers
7. Select “Stack Images”
8. Click “OK”

File -> Automate -> Photomerge -> “Browse” for files:

Edit -> Autoblend Layers -> Select “Stack Images”

With some further tweaking (Merge Layer & Levels Mask)