Give the kings indian a chance....... you might like it. When I had no time to study much I used it against everything other than 1 e4 ......
What to play against 1.d4 and 1.c4

I play the Leningrad Dutch my self. It is, as you say, a very fun and aggressive opening and i can only recomend it. I have a book by Valeri Beim called "Understanding the Leningrad Dutch" which tells you pretty much what you need to know to play the leningrad, and have lots of annotated games. try it out! ^^

It's just not my style to spend the game defending an isolated d pawn.
I can't advocate for the Tarrasch in general, but this statement jumped out at me. The isolated d-pawn structure is an active attacking structure. It is covered in detail in Alexander Baburin's book "Winning Pawn Structures" (a bit over named as it deals almost exlusively with isolated d-pawn structures). The first seven chapters cover attacking ideas for the side with the isolani, presenting several GM level games on a particular attacking motif in each chapter. In short, there are lots of attacking ideas when you have the isolani.

What's with the thread necromancy? I started this thread 14 months ago, and someone suddenly posts in it for the first time since 2008 for no reason. At this point, I've been happily (mostly) playing the Classical Dutch for about a year.
I've thought about learning to play IQP positions better and switching back to the Tarrasch, at least some of the time. But I'd want to get a good reference on IQP positions and go through that first, and I've had other priorities.
But one other thing that really bugged me about the Tarrasch is the symmetric variation. That's the line where white refuses to initiate any trades. Ever. It's kind of like the Giuoco Piannissimo, with the pawns on d4, d5, e3, and e6 instead of e4, e5, d3, and d6. Only more boring.
This is the main reason I can't imagine ever playing the Tarrasch (or Giuoco Piano) as black ever again. Both of these openings have a suck-every-bit-of-life-from-the-game-of-chess variation, and it's worth avoiding any possibility of ever getting stuck across the board from an opponent who would play that way.

I agree with the previous poster. If you think about "defending" the IQP in the Tarrasch, you're already lost! Think about using it for the attack! Aside from the excellent book that the previous poster cited, there are a some really good videos here on chess.com (by Daniel Preuss, I think) covering all aspects of handling IQP positions. The first two or three lessons highlight the strength of the IQP, and should inspire you to give the Tarrasch another go.
I actually disagree with you two, and guess why: because the Tarrasch is a black defense!
The fact that black is down a tempo COMPLETELY changes the nature of the typical IQP, usually owned by white. Black's bishops are often forced to more passive posts, like e7 and e6, and although black's pieces aren't any less active than white's, obviously you need overwhelming activity to have full compensation for the isolated pawn. Either that, or white has to play a serious mistake to get real chances. Plus white early on has serious threats to actually win the pawn sometimes (his bishop on g2, knight on c3, and possibly bishop on g5 as well as on the d file), which helps to compromise black's pieces.
So I think white gets a stable edge in that defense without much difficulty.
From white's point of view on the other hand, I totally agree. It's amazing the difference a tempo can make! In the reversed dragon sicilian white has good chances for a small edge where in the regular dragon black really has to worry about his king in exchange for some counterplay.
So I'm a fairly aggressive, attacking player. As white, I play the Evans Gambit, Smith-Morra Gambit, and 150 Attack. They may not be the best openings out there at the grandmaster level, but they're sound enough against any opponent I'm likely to face (up to 2000 USCF), and most importantly, they're FUN.
Against 1. d4 as black, I used to play the Englund Gambit, but as I improved, I found that higher level opponents don't let me get away with it. It's just not good enough to use against players rated 1800 USCF or higher. I switched to the Tarrasch Defense against everything but 1. e4 as black, just to minimize opening study, but I don't like the type of games that result. It's just not my style to spend the game defending an isolated d pawn.
So I'm looking for aggressive alternatives. I'd prefer one opening that I can use against both 1. d4 and 1. c4, since I see them both a lot lately and I'd like to cut down on opening study, but I'm willing to try out openings that only work against one or the other and continue to play the Tarrasch some of the time, if I find an opening I really like against one of them.
I've heard that the Leningrad Dutch is fairly aggressive and usable against everything. It seems VERY different in style from anything else I've ever played, though, so I'd probably want a good book that explains the key concepts. Anyone think this is a good opening for me to try? Any book recommendations for learning it?
Any other suggestions?
--Fromper