pen
prison
present
phenomenon
passion
possession
padpaidpatternedpacedpallidperfumedperfomedPISSEDplaidpleadplatedpinnedpinedpiledplodplacedpodpostedportendpooledprayedproportionedpreparedpreferredpromptedpromotedpremieredpreviewedpastedpriedpretendpressedproceedputrid
Pan, Pain, Pin
zapp
papaw, pilaw, pshaw
phlox parallax chicken pox pix phalanx
There's only 1! - "PLUMB"
plow
Keep and kelp are four letter words starting with K and ending with P.
nap, newsgroup, nightcap, nincompoop, nip, nonpartisanship and nonstop
pulp prop
Pregnant :P
Words starting with R and ending with P are:raindropreceivershipramprapraspreaprecaprecouprelationshipripromprump