Center on Canvas – Both (No shortcut)
Centers the selected object(s) on the canvas, both horizontally and vertically.
Center on Canvas – Horizontal (No shortcut)
Centers the selected object(s) on the canvas, horizontally.
Center on Canvas – Vertical (No shortcut)
Centers the selected object(s) on the canvas, vertically.
Space Horizontal (No shortcut)
Distributes the selected elements horizontally, with the same distante beetween them.
Space Vertical (No shortcut)
Distributes the selected elements vertically, with the same distante beetween them.
Documentation
Blogroll
Fireworks Resources
Fireworks Wizards
My Pro-Tip for Fireworks would be to bind the alignments so cmd+option+shift+arrow keys left/right/top/bottom align then also set cmd+opt+shift+home for horizontal alignment and the same + end for vertical.
Sped up my workflow so much
I think the Web Standard set has shortcuts for all of those (command + option + number keys).