Over the last decade, consumer-gripe websites have become an Internet mainstay, a place for customers to share opinions on what works and, mostly, what doesn't.

But how well do the leading complaint websites themselves work? On Monday, an old-fashioned bricks-and-mortar organization, the Consumer Federation of America, delivered a mixed verdict: The best sites are great for helping consumers voice irritation, but not so great for helping them address it.

Stephen Brobeck, the federation's executive director, said the group decided to examine more than a dozen complaint websites, in part because they show up so frequently in Web searches.

Not very long ago, aggrieved consumers had few options beyond griping to friends or relatives, filing a complaint with the Better Business Bureau or state attorney general, or suing, Brobeck said. Now, sites such as My3cents, Complaints Board, and Ripoff Report, offer an alternative.

Though some sites, such as My3cents, offer consumers the chance to post positive comments, the sites have special appeal to the disgruntled.

"They're unhappy, and they want to vent," Brobeck said. "And this is a very low-cost way to vent, with potentially high impact."

The report identified six sites as "especially popular and potentially useful": Complaints.com, My3cents.com, ComplaintsBoard.com, PissedConsumer.com, ConsumerAffairs.com, and RipoffReport.com.

It singled out My3cents on several grounds, including its high volume of recent postings and its inclusion of tips on resolving complaints - a rarity among the sites.

"In an ideal world, these websites could be much more robust," Brobeck said. He said the federation even considered urging improvements before it "came back to reality. These are pretty much one-person websites."

Susan Grant, the federation's director of consumer protection, said the best sites could help potential customers of the large, national companies most likely to appear in the sites' databases.

She said a lack of complaints should not be seen as any sort of guarantee. "But if there are lots of complaints, and lots of complaints about particular kinds of problems, that's a good indicator to consumers that they may want to look elsewhere for their purchases," Grant said.

Grant said the sites could also prove useful because consumers sometimes shared stories about how they ultimately solved a problem.

Brobeck said the study found no evidence that consumers - or corporate competitors - were filing false complaints. Nor was there any reason people should worry about retaliation, in part because truth is a defense against an accusation of libel.

"If people just stick to the facts, and tell the story as objectively as they can, we believe the chance of retaliation is minimal," Brobeck said.

Several large businesses told the Consumer Federation that they monitored the sites, along with other public mentions of their companies. Consumers who hope their venting could prompt a response may want to consider using one of three sites that allow complainants to edit or remove postings: My3cents, ComplaintsBoard.com and Complaints.com.

And the federation said consumers who want help resolving complaints, or broader-based information about companies, should consider the old-fashioned approaches: complaining to a consumer protection agency, and reading evaluations from independent sources such as Consumer Reports, Consumers Checkbook, or Angie's List.

To see the federation's report, go to http://go.philly.com/cfa.

Contact staff writer Jeff Gelles at 215-854-2776 or jgelles@phillynews.com.