I play guitar and am even more obsessed with guitars, amps and effects than I am with guns, so there are 2 guitar forums that I frequent:http://www.rig-talk.com/forum/index.php ... 26eb33eb66
RT is a great site for knowledge and gear reviews, and also for deals...the guy that owns the forum also owns a high-end boutique shop in CA and RI called http://www.kingguitar.com
There are great deals to be had...if you want musical equipment and can't buy/find a review of it on RT, it doesn't exist. Watch your wallet; stuff gets spendy there...this is a site for metal and 80s rock and that's what most of the equipment is geared toward.http://www.mylespaul.com/forums/
This one is more blues/rock based, with Les Pauls being the main focus(I'm a junkie, I admit it)although they do have other sections for PRS, Fenders, and 'other' LPs, mostly higher end Japanese imports from the 70s up until yesterday...the Backstage(off-topic section)is a blast and moves VERY fast, and this forum also has a feature called 'spy' which is a link you can click to see topics update in real time...the Afterhours section is NSFW.
Other than that, I come here and OpenCarry.org....was a member of a few other guitar forums and Facebook, but the drama got old so I usually just hit these and call it good.