I know there are two other shorteners but I did this as a hobby project and to add to my portfolio. Now your probably asking why use my shortener then any other shortener, lets explore this together. First off if you look at
http://payb.tc how do you know how your addresses and short name are stored? I am guessing plain text. Quick Coin Lookup doesn't store any addresses with the short name in plain text. It stores the short names in a hash format, just like a password. It using a hash and a salt, so if a hacker gained control of the database they wouldn't be able to find your short name just by looking at it. Now storing the address took a little more cleverness, it is stored in AES-256 encryption using the short name and salt as the key. So now you know your addresses aren't able to be changed, easily by a hacker, plus the system is self alerting, it can tell if the AES and short name don't match alerting the users, and will not display the decrypted address. Plus the domain name is shorter.
Now moving on the next shortener is the Mt Gox
http://btc.to. BTC uses first bits which is encouraging spamming the blockchain, that is inappropriate just for the purpose of a shortener. Also it doesn't support litecoins or more than one explorer which QCL does both.
Other features, one click copy (Flash and Javascript), Only address shortener that supports link to open address in clients that support it, includes qr code on the page in a big picture, blocks spammy short names to not be confused, only can register one address and short name a day so you can't spam or take all the short names.
http://qcl.me/http://qcl.me/faq for more information
http://qcl.me/api/ for information about the simple API
http://qcl.me/donate or
http://qcl.me/gweedo for what an address page looks like
I would gladly add other altcoins so leave it in the thread. (Important point, to have altcoins added it must have at least one block explorer and the address should be different from a bitcoin address.
Leave any other questions, comments, feature request in the threads...