Salsa (also known as Democracy in Action or DemocracyInAction, and Wired for Change) products are a cheaper alternative to ActionKit for groups that have an in-house tech team and want to do a lot of custom coding and work with plug-ins. The product has a complex user interface and is frequently used with Drupal or WordPress for a CMS and Ning for a social network, and requires a lot of integration work as a result. They have an email-your-legislator “spank and thank” tool at the federal level, and if that is important to you, you may want to consider it (NationBuilder recommends PopVox for federal advocacy).
Salsa's products are only for progressives, and they don't have NationBuilder's voter outreach tools and data such as the voter file, call and walk lists and turf cutter. For voter outreach, people will generally use NGPVAN with Salsa. Adding up all the additional tools needed and custom integration, it ends up being quite expensive. NationBuilder's transparent pricing makes the tools of democracy open to all, and we include a 14-day free trial.