Oh oh!! I forgot my favorite Simpsonism of all time!
“Call me mint jelly cause I’m on the lam!” (Grandpa Simpson)
For some reason, the line really tickled me, and I’ve actually used it a few times, although -totally- out of context. 
I forgot this one:
Sax-a-ma-phone! (Said a la Beethhoven’s 5th)
Whenever someone says, “I love XYZ,” someone has to respond, “Is that like the love of a man for a woman, or the love of a man for a fine cigar?”
Also, when someone’s giving directions, “Oh, do you mean the hammock district?” is always good for a larf.
And the “Monorail! Monorail! Monorail!” chant is sure to come up in any discussion of public transporation.
Homer’s “I’m going out to commit certain deeds” (from the episode where he’s supposed to leave Moe’s car on the railroad track for insurance money). Not that I would ever dream of committing “certain deeds” myself. The line is just funny to me, especially when I wear one of my black bank-robber hats.
Also, I use Nelson’s “ha-ha” quite a bit.
On a slightly related note, I have observed over the years that just about any and every occurrence in life, big and small, can be referenced to some Simpson’s plot, scene, or quote. I guess that is the genius of the show.
LOL…I almost forgot about this one: I have secretly nicknamed one of my coworkers “Selma and Patty”. Because she smokes, looks and talks just like…well, you get the idea.
Oh yeah, two more…
When I leave a room, I try to yell out, "If I’m not back in an hour, avenge my death!"
When someone says something that I just don’t understand, I’ll give 'em a, "You’re selling what now?"
My favorite Smithers employee euphemism is “fork and spoon operator.”
This is also a favorite away message of mine: "But Marge, we’re college guys and we’re up to no good!
Not quite what the OP had in mind, but whenever I belch I always try to say “Ralph Wiggum”
I think the quote is (cause i say it everytime i leave the house)
“Going out, if not back avenge deaths.”
I love the Dr. Hibbart quote about the love, use that one often. Frankly anytime someone says anything that reminds me of the simpsons I use it …
When running a red light or coming close to it I always cover my eyes and go “If I don’t see it, it isn’t illegal” 
“Forty seconds, but I’m hungry now!”
“Rock and/or roll”
I refer to any of THAT type of restaurant as “TGI McScratchy’s”
“We started out like Romeo and Juliet, but it ended in tragedy!”
“Lousy Smarch weather”
“Your not as objectional as you seemed when we first met”
“Computers can do that!”
“I’ll deal with those murderous trolls”
I cannot believe nobody else has cited this one…everyone in my school says Jeebus instead of Jesus.
Also, of course, the D’oh and the Ha-ha, and I’m partial to the use of Eeexcellent. And whenever anyone does a sexy wiggle in my family, my dad says, “Nothin’ at all…nothin’ at all…nothin’ at all.”
Embiggen has become a real word to me.
And, dude, I agree with tarragon’s “Call me mint jelly, 'cause I’m on the lam!” comment. I don’t know why it makes me laugh so hard, but it always does.
And we snotty California school children came up with an answer to Smarch–Graydavisember, named after our governor who said he was going to expand the school year by a month.
Along with the a good portion of the previously mentioned…
Ralph - “I think I broke my Wookie”
Homer - “I’m going…OUT…to stalk…lenny and karl…DOH!!!”
Bart(with funny voice) - “Its a cow’s heart, They’re trying to make a monkey out of you”
The smart girls dad from the same episode above to Lisa- “I have a ball. Perhaps you’d like to bounce it?”
I have found that “He’s gone mad with power like that Albert Schweitzer guy” is useful. Especially when referring to people who have gone mad with power. Like that Albert Schweitzer guy.
And of course “Nobody likes Milhouse!” and “Everything’s coming up Milhouse!”
And any stupid argument can be countered with “This rock keeps away tigers.”
Actually thats “I bent my Wookie” whenever I fall skating or whatever, I use that line.
“cat in the furnace.”
“Stealing, stealing stealing a car for Moe,
da da da da, da da da da, insurance fraud today!”
“that’s what happens when you don’t hail to the chimp!”
“Save me Jeebus!!”
I use Nelsons “Haw-haw” atleast 2times a day, usually in the voice too. Burns-style Excellent and Doh are used also, but not to the same extent. Also, whenever I see my friend Chris, another avid Simpsons fan, I greet him with “Hi Supernintendo Chalmers!”
When frustrated:
Why must life be so hard? Why must I fail at every attempt at masonry?
The normal ones: “D’oh,” “My cat’s breath smells like cat food.”
I also try to work “Bonjourrrrrrrr, you cheese-eating surrender monkeys!” into conversation as frequently as I can.
“Stupid. That’s why everybody does everything!”