Nice tip from TUAW : Add recent Applications … simply

> defaults write com.apple.dock persistent-others -array-add '{ "tile-data" = { "list-type" = 1; }; "tile-type" = "recents-tile"; }'

> killall Dock

if you’ve mis-typed and the Dock would no start again you can remove this domain(com.apple.dock) and key(persistent-others) by using

> defaults delete com.apple.dock persistent-others

and redo the above…. you can also use

> defaults read com.apple.dock persistent-others

to see the current values

defaults man page and more excellent tips from MacOSXTips.co.uk