Here is an other 100% Free Dating Service. Introduction from their main page:               

'Join other singles browsing our online personals on this totally free dating service. Join thousands of sexy men and sexy women who have discovered Online Dating and found their perfect match via matchmaking. Below are ads from great cute online singles looking to chat and meet you at Plenty of Fish ...'

Currently it appears that Plenty of Fish is the fifth largest dating site in North America based on daily unique logins. Plenty of fish.com sparks fear in the heart of the online dating industry. This week alone 100,000 daily unique logins exceeded the previous record of 50,000 daily unique logins of only three months prior. Match.com, Yahoo.com, Eharmony.com and Americansingles.com are the only other dating sites suspected to surpass it.

It is free, as in completely free to message each other, email each other, look at profiles, browse, search... The only problem with Plenty of Fish is that there are not a huge amount of people on it. By the way at no point during the registration process does it ask you for anything like a credit card number or anything, so there are never any charges.