I wrote a little applescript to answer a ringing Skype call, so I can answer calls from the keyboard (by way of a quicksilver trigger).
tell application "Skype"
set calls to send command "SEARCH ACTIVECALLS" script name "Call Control"
set callID to last word of calls
set status to send command "GET CALL " & callID & " STATUS" script name "Call Control"
if last word of status is "RINGING" then
send command "ALTER CALL " & callID & " ANSWER" script name "Call Control"
Put this in a file in your ~/Library/Scripts folder, and make sure quicksilver is indexing it. Then you can add running the script to a hotkey using a trigger.