Lisa Loopner
Lucky Luciano
Lyle Lovett
Lucky Lindy
Loma Linda
Lurleen Lumpkin
Loser’s Lounge (can you tell I’m watching Celebrity Poker Showdown?)
Lola Lola
Gee, I could have sworn it was in Alberta.
lefty loosey
little lady
lounge lizard
long lost (as in “He was my long lost brother!” or some such thing.)
last laugh
Larry Linville
Damn! Guess I had a little lapse. :wally
Lincoln Logs
Lisa Loeb
Lorelei Lee
Lucy Locket (lost her pocket)
Lafayette Leopards (college sports team)
Limousine Liberal (probably too long, I realize)
Lay Lady Lay (a triple!)
How could I have not come up with this one before?
Literary Lapses (by Stephen Leacock, available from Project Gutenberg and on paper from Amazon.
This is probably too long, but I would suggest the SDMB’s very own Laughing Lagomorph.
liver lips
Loretta Lynn
Lancelot Link
little league
Lightning Lad
Movies:
Lacombe, Lucien
Liar Liar
Libeled Lady
Not to mention my wife’s name (prettier than any of Superman’s girlfriends) 
BUZZZZZZZZZ Time’s up, ladies and gentlemen!
Okay, here’s the list in its final form:
Louis L’Amour
Lover’s Lane
Little Lulu {rjk}
Laundry list {rjk}
Louie Louie {matt_mcl}
Lemon-lime {matt_mcl}
Lady Luck
Latin lover {rjk}
Lounge lizard {MissTake}
Last laugh {scribble}
Little league {ArchiveGuy}
And, as always, the decision of the judges – er, judge – is final.
Winners: If you’d like a copy of the cryptograms magazine this will appear in when it comes out, email me (twickster47@yahoo.com) with your IRL name and address.
Whoo. That was fun. Want another one?
How 'bout – JJ?
Janet Jackson
Jumpin’ Jehosophat
…
Damn. Always the bridesmaid, never the bride.
Jessie James
Johnny Jumpup
Js are more difficult.
James Joyce
Should I give the honorable mention list, or would that be rubbing salt in your wounds? I really liked “liquid lunch.”
That mention is sufficient to make me smile.
Java Jive (song by the Ink Spots)
Nice one!
Judge Judy.
Janis Joplin
Here’s one if you really want a stumper:
Jose Jimenez (comedic character played by Bill Dana, but upon a Google there is also a ballplayer with this name)
No no, I’m not at all upset that I didn’t make the cut…
Jake Johansen (comedian, not sure of the spelling of the last name)
Jimmy Jam (music producer, partnered with Terry Lewis)
Jimmy James (Great Escape)