In this case, a “Carnival” is a weblog post that brings attention to some of the week’s most interesting and informative blogger-written articles within the broad spectrum of personal finance. It is a showcase of weblog posts, submitted by their authors or by casual readers for consideration.
Some of the topics considered for inclusion are budgeting, saving money, earning money, managing debt, living below your means, and any other topic somewhat related to personal finance.
Flexo is the founder of Consumerism Commentary and the Carnival of Personal Finance. 
I recently entered the bloggin world and was scratching my head when I saw all these references to carnivals. Thanks for clearing up the fog. I look forward to submitting Personal Finance articles in the future.
Cheers!
– Josh