This plugin lets you grab image layers from any PSD/PSB file. It's faster than opening the whole PSD in Photoshop, if you just want a layer. Also, it lets you open PSD created by the newest versions of Photoshop, in older Photoshop versions that cannot read them directly. Most importantly, it can usually recover image layers from corrupted PSD files that Photoshop won't open (if Photoshop opens with damage, this plugin recovers a more intact image).
FREE - small donation suggested if it saves your day/sanity/job.