I like the fact that you can mine other currencies concurrently with your bitcoin mining on Bitparking. It's like a little extra cash at the end of the month when I combine them and trade them for BTC's
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I do not know of any other mining pools that allow you to mine 4 different currencies at once. If there are any, please let me know.
Can you explain what you mean by "at once"? If you use your GPU for one, you are not using for the other. In other words, while your GPU is mining namecoins, it is
not bitcoins, and vice versa. So, unless namecoin is more economic to mine, you are actually losing money when use your rig for mining something other than bitcoins. And if namecoin is more economic, then one should be mining that all the time.
Am I missing something?
By the way,
http://coinotron.com has a large variety of coins to mine.