Some work, some are just scams. First thing to know is that a "Credit Repair" service that is legitimate, is only going to do things that you can do yourself. The benefit of using one of these services is that they already have the knowledge and they will put in the time for you. The process of "repairing" ones credit is very time consuming and requires strong knowledge of the Fair Credit Reporting Act (FCRA) as well as the Fair Debt Collection Practices Act (FDCPA). What a legitimate service will do is contact the creditors directly and challenge the validity of the debt, the reporting of the debt, and the agencies acquisition of the debt. If the reporting agency has not followed the guidelines set forth by the 2 Acts listed above, they will most likely remove the mark from your report. A legitimate service will also dispute the debt's directly to 3 major credit bureaus. To answer your questions, yes, they can work but you have to be careful. Just make sure you are getting in with a legitimate service. Check the BBB and ask for references.
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debt consolidation

if someone wants to get out of debt today it is pretty easy with a debt consolidation plan
however it may get a bit tricky at times, I suggest you get as much information as possible online on this first,

a good place to start in my humble opinion is:

http://umgarticles.atspace.com/debt-consolidation.htm
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