Woah I've been gone for a long time. Let's settle this trekkie/trekker debate. Now then both titles seem rather meaningless because the wide diversity of Star Trek fans can't seem to agree what the defination of either are.
Some people claim the difference from trekkie and trekker is trekkers are OGST(Original (Gangsta) Star Trek in other words TOS fans) and trekkies are fans of TNG. Apparently Trekkers watched the show when it was originally aired(or prior to the release of TNG or the motion pictures) and are thereby superior to all star trek fans. Trekkies are people who jumped on the band wagon after TNG was aired and of course there are Niners who are fans of DS9 and I have no freakin clue what they call Voyager or Enterprise fans(if there are in fact any Enterprise fans out there).
Now with that definition out of the way we have the next one that also deals with quite a bit of elitism. Some fans claim that trekkers are casual fans who can even been seen at conventions but just like the goofy squares at Ren festivals they don't dress up in appropriate attire. Trekkies are the hardcore dorks who show up in starfleet uniforms and vulcan ears and forehead ridges and leather and computer components like they went shopping at a circut city that also sells fetish wear. In this definition trekkie is used as an insult.
And then there are people like me and apparently Gene Roddenburry who dismiss the trekker title and call all star trek fans trekkies. I.E. at a star trek convention long ago Roddenburry let the word trekkie slip and a member of the auidence yelled back "it's trekkers" to which roddenburry replied "it's Trekkies I should know I invented it."