1. Go to those gazilllion sites and insure the data regarding this listing is not altered...every month. Not a good option.
2. Select websites not appearing on the syndication list and are compatible with your real estate for sale inventory and enter your data there.
Be sure to check with the CRM system you use with your real estate business. Many of them have easy posting tools for Craigslist, Facebook, Twitter and other sites. Point2Agent, for instance, has an incredible portfolio of syndication sites you can selectively enable.
If I were you, I would contact a local Realtor, have them visit me for a free consultation to get their thoughts on the comparison between locally available "flat fee" brokerages and a traditional Realtor's more comprehensive services.
Good luck either way!