Paste clipboard data as plain text Service?
A couple options, gleefully swiped from Mac OS X Hints:

Applescript, converting pasteboard contents to plain text and pasting: 

tell application "Finder" to set frontApp to (name of 1st process whose frontmost = true)
tell application frontApp
    activate
    set clip to «class ktxt» of ((the clipboard as text) as record)
    tell application "System Events" to keystroke "v" using {command down}
end tell


Shell script, save it in your Scripts folder and chmod 755

#!/bin/sh
pbpaste | pbcopy
osascript -e 'tell application "System Events" to keystroke "v" using {command down}'