I use PR Web a lot, usually paying at the $30 level which has resulted in the story being picked up by search engines really well. The Google links appear in the Search Web rather than the News part of Google and they seem to last forever. Prior to Christmas 2 years ago I put out a release about the free online crossword puzzle we were giving as a gift to our visitors and if you search on the words financial and crossword, or similar, the story still comes up.

The 2 big news release services are PR Newswire and Businesswire. They both charge an annual fee as well as a per-release fee. A distant 3rd is MarketWire (formerly Internet Wire). However, it is starting to give the 2 major players some real competition. It does NOT charge an annual fee. Also it has become a "NASDAQ Preferred Partner" or some such designation and is really going for the financial press release business.

When looking for a release distribution you should also compare various services' specialized coverage of your industry or your interest area.