Gah, so many. How about I list the highlights of all the main albums? using the list from
http://www.weirdal.com/catalog.htm starting at the bottom of the studio albums section and going up (I won't mention polkas, most of those are good though):
-Ricky, I Love Rocky Road, My Bologna, Another one Rides the Bus, Such a Groovy Guy
-Eat It, The Brady Bunch, I Lost on Jeopardy, Theme From Rocky XIII, one line of Nature Trail to Hell When it's played backward (dang, that was a clever easter egg)
-Dare to be Stupid, One More Minute, Yoda, Girls Just Want to Have Lunch
-Addicted to Spuds, Here's Johnny, Good Enough for Now, Christmas at Ground Zero
-Fat, I think I'm a Clone Now, Lasagna, Alimony, Good Old Days
-Beverly Hillbillies, UHF, She Drives Like Crazy, Spam, and apparently Biggest Ball of Twine is good but I haven't heard that because I don't have the CD (I have the movie, but the song isn't in it). I have actually seen the biggest ball of twine, though.
-Smells Like Nirvana, Trigger Happy, I Can't Watch This, When I Was Your Age, Taco Grande, Airline Amy, The Plumbing Song, You Don't Love me Anymore (that's a pretty good CD

)
-Jurassic Park, Bedrock Anthem, Frank's 2000" TV, Achy Breaky Song, Livin' in the Fridge, Harvey the Wonder Hamster, Young, Dumb, and Ugly
-Amish Paradise, Everything You Know Is Wrong, Cavity Search, Since You've Been Gone, Gump, I'm So Sick Of You, Syndicated, Inc., I Remember Larry, The Night Santa Went Crazy (another especially good album)
-The Saga Begins (quite possibly his most famous song nowadays, every kid in my school knew this when I was in second grade), Pretty Fly for a Rabbi, The Weird Al Show Theme, Your Horoscope For Today, It's All About The Pentiums, Grapefruit Diet, Albuquerque
-Hardware Store, Party at the Leper Colony, A Complicated Song, Ode to a Superhero, Bob, eBay, maybe Genius in France
-White & Nerdy of course, Canadian Idiot, Weasel Stomping Day, Close But no Cigar, Do I Creep You Out, Trapped in the Drive-Thru, Don't Download This Song
Your mind=blown.
If I had nothing better to do, I'd provide imeem links and give you the lyrics from memory
*runs and gets CD collection to listen to some of these*
EDIT: Sifted through the parodies mistakenly attributed to Al on imeem, and found a song that's actually his that most people haven't heard.
<div style="width:300px;"><object width="300" height="110"><param name="movie" value="http://media.imeem.com/m/I4kP618nT1/aus=false/"></param><param name="wmode" value="transparent"></param><embed src="http://media.imeem.com/m/I4kP618nT1/aus=false/" type="application/x-shockwave-flash" width="300" height="110" wmode="transparent"></embed></object><div style="background-color:#E6E6E6;padding:1px;"><div style="float:left;padding:4px 4px 0 0;"><a href="http://www.imeem.com/"><img src="http://www.imeem.com/embedsearch/E6E6E6/" border="0" /></a></div><form method="post" action="http://www.imeem.com/embedsearch/" style="margin:0;padding:0;"><input type="text" name="EmbedSearchBox" /><input type="submit" value="Search" style="font-size:12px;" /><div style="padding-top:3px;"><a href="http://www.imeem.com/ads/banneradclick.ashx?ep=0&ek=I4kP618nT1" rel="nofollow"><img src="http://www.imeem.com/ads/bannerad/152/10/" border="0" /></a><a href="http://www.imeem.com/ads/banneradclick.ashx?ep=1&ek=I4kP618nT1" rel="nofollow"><img src="http://www.imeem.com/ads/bannerad/153/10/" border="0" /></a><a href="http://www.imeem.com/ads/banneradclick.ashx?ep=2&ek=I4kP618nT1" rel="nofollow"><img src="http://www.imeem.com/ads/bannerad/154/10/" border="0" /></a><a href="http://www.imeem.com/ads/banneradclick.ashx?ep=3&ek=I4kP618nT1" rel="nofollow" ><img src="http://www.imeem.com/ads/bannerad/155/10/I4kP618nT1/" border="0" /></a></div></form></div></div><br/><a href="http://www.imeem.com/people/PLkjon/music/o4kjfZXb/weird-al-polkamon/">Polkamon - Weird Al</a>