The dialog I use most often, by far, is Align and Distribute.  So I have assigned the most frequently used alignment operations to the keypad keys:

• 5: Center on h and v axes
• 8: Align top edges
• 2: Align bottom edges
• 4: Align left edges
• 6: Align right edges

• *: Align bottom to anchor top
• /: Align top to anchor bottom
• -: Align right to anchor left
• +: Align left to anchor right

• 7: Paste size (HW) from clipboard 
• 1: Paste height from clipboard
• 9: Paste width from clipboard
• 3: ObjectRotate90

Version .91 does not allow keypad keys to be specified on the keyboard preferences page.  To utilize these keypad keys, it is necessary to add them to the ~/.config/inkscape/keys/default.xml file:

  <bind
     key="KP_5"
     action="AlignVerticalHorizontalCenter"
     display="true" />
  <bind
     key="KP_8"
     action="AlignVerticalTop"
     display="true" />
  <bind
     key="KP_2"
     action="AlignVerticalBottom"
     display="true" />
  <bind
     key="KP_4"
     action="AlignHorizontalLeft"
     display="true" />
  <bind
     key="KP_6"
     action="AlignHorizontalRight"
     display="true" />
  
  <bind
     key="KP_Multiply"
     action="AlignVerticalBottomToAnchor"
     display="true" />
  <bind
     key="KP_Divide"
     action="AlignVerticalTopToAnchor"
     display="true" />
  <bind
     key="KP_Subtract"
     action="AlignHorizontalRightToAnchor"
     display="true" />
  <bind
     key="KP_Add"
     action="AlignHorizontalLeftToAnchor"
     display="true" />
  
  <bind
     key="KP_7"
     action="EditPasteSize" />
  <bind
     key="KP_9"
     action="EditPasteWidth" />
  <bind
     key="KP_1"
     action="EditPasteHeight" />
  
  <bind
     key="KP_3"
     action="ObjectRotate90"
     display="true" />
 

A few of these alignment shortcuts are included in v.92.2.

Versions .92.xx and higher are recommended, as they include the scale change from 90dpi to 96dpi, in alignment with the changes to CSS by the W3C. (Along with some great features.)