Your best option is to list all the 45s you want to sell here, in this forum, with the "I will accept the best offer" tag for each 45 - unless you have a desired price in mind. You will get a fair price for most of your sought-after discs; common $10-$30 45s will be hard to sell unless they are priced far below that. As you know, accurate grading is most important.
If you do decide to list your collection here, i would post an announcement first, long before you post the actual list, to give members a "heads up". It is also best not to clash with the set sale offerings posted by forum member, dr. punk, who has been posting set sale lists from a massive garage collection sell-out over the past few months
Ebay is the place to sell if you have the time, and the patience. If you put up a rare 45 be sure to place it in the proper main and sub categories - the garage rock category, list as a 45rpm / 7 inch, etc. Otherwise, you run the risk of bidders missing out on seeing your auction and the 45 will sell for much less than the potential worth. This just happened with the Chancellors "On Tour", a 45 that is at least $1,500 in strong VG+ condition - a copy was won on ebay for $286.