If you are looking for a great fanfiction con to go to, I recommend Eclecticon over Media West. Having run conventions myself, I know what it takes to make them come off and Kathy Agel and her staff know what they are doing. It is a friendly con. There is a lot to do and plenty of time to just relax and converse with other fans. Those are the only two on the list I have attended personally, but Revel Con, Rocky Mountain Media Con, Vidcon and Shore Leave are all cons I know of and would recommend on the basis of the people running them.
Connexions is an all slash con.
Attendees must be over 18.