SEO Roadshow – Free once a year non-commercial bar meetings. They are free and uber cool…need an invite to go though. NFFC is cool.
Search Engine Strategies – Geared more toward the marketing and advertertising professions, these are usually ran by Danny Sullivan of SearchEngineWatch. Host about 8 to 10 of them a year. about $1,700 for a 4 day conference (some local SES conferences are shorter and cheaper – also if you register early you save $100, and if you hunt you can usually find a coupon to save a couple dollars on the entry cost).
WebmasterWorld Conference – Geared more toward the independant webmaster, these are hosted by Brett Tabke of WebmasterWorld. Occurs about 2-3 times a year. about $500 to $1,000 for a 3 day conference (price depends on when you buy, which conference you attend, etc.).
ThreadWatch Conference – Similar to SEO Roadshow, with much overlap in who attends.