I'll actually start things out with the Professional Association I belong to. Please don't take this as a self-serving attempt on my part to get more members in my Association. It's merely an interest on my part and something I think the industry needs.
The Association of Ontario Land Surveyors has a GIM desgnation (Geographic Information Management - follow this link to the full description) that gives GIS practitioners a home. We have a code of ethics, practice standards, peer review, group liability insurance, etc. I've found that a true professional designation (as opposed to belonging to an industry or related association or having a certificate) has enabled me to hold myself out as being held accountable by my peers and my Association. This in turn has helped me and my company land projects of a high regulatory interest - E911 mapping, for instance, where mistakes can cause injury or death.