The problem with other ad-blockers for Safari is that they are implemented as awful hacks: as an InputManager and/or ApplicationEnhancer. This compromises the stability of Safari and very often create problems when Apple releases a new version of Safari.
GlimmerBlocker Features
DiscontinuedThe project seems to be no longer developed. Last version, 1.6.6, released in September 2015, can be still downloaded from the official website.
Top 3 alternatives