Here are some journals that very frequently solicit my expert opinions, without really checking whether I have the expertise or not, and without any impact factor.
Resources I use to check the credibility of unknown journals:
Founded in Cairo in 1997.
22 of the 300 journals have an impact factor higher than 0, but below
Some other researchers impressions: http://list.uvm.edu/cgi-bin/wa?A2=MEDLIB-L;wGArog;20110726180255-0700d
I have been solicited to write an expert article for the following journals the past year. Even though I feel flattered, I would not think too much of researchers that publish in these journals with zero impact factor (and not because they are too new!)