Same here-> Bob once emailed me a list of them (copied below, but they're from v4.0 so out of date) - 
A current list of all shortcuts is definitely key and should be easily accessible in the documentation, and straight from within the program. (I know they're listed in the menu, but a comprehensive list is useful)
-jj
***********************************
  Here are PM v4's keyboard shortcuts :
  ========   keyboard shortcuts for PM4 Mac contact sheet : ========
 
Cmd  A    Selects All of the thumbnails in the open contact sheet
   "    D    Deletes the selected thumbnails
   "    E    Sends the selected thumbnails off to the secondary editing application
   "    H    Hides the Photo Mechanic application
   "    I    Opens the IPTC Stationary Pad for batch updating the selected TN's
   "    L    Starts the Slide show on the selected images
   "    M    Rename the selected TN's
   "    N    Opens a new blank contact sheet
   "    O    Opens the Open dialog
   "    P    Starts the Print utility - Contact sheets & Proof pages
   "    Q    Quits the Photo Mechanic application
   "    R    Opens Preview window on the first selected TN
   "    S    Starts Save Photos As utility - tiff & jpeg files
   "    T    Selects all Tagged TN's
   "    W    Closes the open contact sheet
   "    Y    Starts the Copy Photos utility
   "   [    Rotate selected 90 CCW
   "   ]    Rotate selected  90 CW
   "   +   Tags  selected TN's
   "   -    Un-tags the selected TN's
       C        Toggles color management status
  Option-Double click a thumbnail will send it to secondary editing application ( Photoshop)
========================PM v4 Mac Preview Commands ==================
All of these commands are the single keys. The minus sign is the bullet
-   <right_arrow> move to next image
-   <left_arrow>  move to previous  image
-   -           unselects current image and moves to the next selected image
-   [             rotate 90 CCW
-   ]             rotate 90 CW
-   T             toggle tag status
-   Z             zoom to full screen
-   R             regular preview
-   I             open IPTC Info dialog
-   E             edit in secondary application ( photoshop or .. )
-   C            toggle color management status
-   H            horizontal two up configuration
-   V            vertical two configuration
-   <Esc>         exit preview screen
=====================PM  Slide  Show  Mac  ========================
  <left-arrow>    : back up one image
 <right-arrow>   : next image before time out
  Space-Bar        : next image before time out
  Caps-Lock        : pause the show
  += key             : Tag the image
  _- key                    : un-select the image
  esc key            : exit the show