Are there legitimate credit cards that can help rebuild credit?

Can you answer Sniggly_Snew’s question about Credit Repair?:

I have a Reward Zone credit card that I’m using to help rebuild my credit. From what I’ve read, I need more than one credit card to help restore my credit. Does anyone know of any legitimate companies that can help improve my credit? And, yes I realize that I must make payments on time, etc. etc.

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