any Beatles song, but if it must be weed related...
Bone Thugs-n-Harmony - Weed Song
Buddah Lovaz <-- Lyrics are hilarious
Blaze It
Afroman - Because I Got High
Just My Paranoia
Kenny Rogers - I Just Dropped In (To See What Condition My Condition Was In) - From the Big Lebowski and about LSD, but lyrics are awesome