user8935: Does anyone know why there are no Scrypt based merged mining pools out their yet? I would imagine that if it was possible it would have been done already. There is no problem to do it with SHA-256 based coins, so why can't we do it with Scrypt?

user13017: The short answer is that there are, but you can't find them because Google is doing wierd things to altcoins in the search rankings.
Orgcoin www.orgcoin.org is a real coin designed to be merge mined with any scrypt chain.  USC is similar in this regard as well.
The primary difference is that Orgcoin is already operating in house pools for LTC, DOGE, POT and any others upon request and is traded on several exchanges. 
At the time of this writing, the current rate for ORG is on par with DOGE meaning you could potentially double your cashflow if you were mining it today.  Not a pump, just a fact.
I'm sure more coins will come online shortly.  But as one of the original posters said.  The primary reason for a coin to merge mine is to secure it's blockchain against a 51% attack.  The child coin needs code for that although the parent doesn't need to know nor care.

user13009: Yes it is possible. Thre is (at least) one spanish pool (http://manicminer.in) mergemining.
You can choose to point your miner to one of  3 main chains (litecoin, dogecoin, potcoin) and you also get Pesetacoin (s spanish cryptocurrency) orgcoin , UnitedScrptCoin and huntercoin.

user8935: Found a helpful post at litecointalk:

It won't work because the aux work must be explicitly provided by the merge coin.  All of these coins cloned from Litecoin lack that code as Litecoin doesn't have it.  As a result you cannot merge mine these coins.
It is the same reason you can't merge mine Terracoin or Freicoin with Bitcoin.  Freicoin considered it in the past as means to stabilize their network, but I'm guessing they decided against it because they are afraid of their value collapsing even more.  Trouble is none of the small PoW coins are able to maintain a stable network if they are subject to sudden reorg attacks at any moment as many of the scrypt clone networks often experience.  Thus avoiding merge coins to preserve "value" is illusory and self-defeating.

Also, apparently there is a scrypt coin designed for merged mining with Litecoin called UnitedScryptCoin, though I didn't have a chance to try it yet. Link to UnitedScryptCoin thread in bitcointalk. 

8935: <p>Does anyone know why there are no Scrypt based merged mining pools out their yet? I would imagine that if it was possible it would have been done already. There is no problem to do it with SHA-256 based coins, so why can't we do it with Scrypt?</p>
 13017: <p>The short answer is that there are, but you can't find them because Google is doing wierd things to altcoins in the search rankings.</p>

<p>Orgcoin www.orgcoin.org is a real coin designed to be merge mined with any scrypt chain.  USC is similar in this regard as well.</p>

<p>The primary difference is that Orgcoin is already operating in house pools for LTC, DOGE, POT and any others upon request and is traded on several exchanges. </p>

<p>At the time of this writing, the current rate for ORG is on par with DOGE meaning you could potentially double your cashflow if you were mining it today.  Not a pump, just a fact.</p>

<p>I'm sure more coins will come online shortly.  But as one of the original posters said.  The primary reason for a coin to merge mine is to secure it's blockchain against a 51% attack.  The child coin needs code for that although the parent doesn't need to know nor care.</p>
 13009: <p>Yes it is possible. Thre is (at least) one spanish pool (<a href="http://manicminer.in" rel="nofollow">http://manicminer.in</a>) mergemining.</p>

<p>You can choose to point your miner to one of  3 main chains (litecoin, dogecoin, potcoin) and you also get Pesetacoin (s spanish cryptocurrency) orgcoin , UnitedScrptCoin and huntercoin.</p>
 8935: <p>Found a helpful post at <a href="https://litecointalk.org/index.php?topic=4768.15">litecointalk</a>:</p>

<blockquote>
  <p>It won't work because the aux work must be explicitly provided by the merge coin.  All of these coins cloned from Litecoin lack that code as Litecoin doesn't have it.  As a result you cannot merge mine these coins.</p>
  
  <p>It is the same reason you can't merge mine Terracoin or Freicoin with Bitcoin.  Freicoin considered it in the past as means to stabilize their network, but I'm guessing they decided against it because they are afraid of their value collapsing even more.  Trouble is none of the small PoW coins are able to maintain a stable network if they are subject to sudden reorg attacks at any moment as many of the scrypt clone networks often experience.  Thus avoiding merge coins to preserve "value" is illusory and self-defeating.</p>
</blockquote>

<p>Also, apparently there is a scrypt coin designed for merged mining with Litecoin called UnitedScryptCoin, though I didn't have a chance to try it yet. <a href="https://bitcointalk.org/index.php?topic=353688.0">Link to UnitedScryptCoin thread in bitcointalk</a>. </p>
