I've been playing guitar since I was 16 years old. That means I've got about a decade of experience. Most of my formal training has been in Classical Guitar at the local Junior College, but I've also taken electric lessons sporadically, and, like most self directed guitarists have a nice stack of instructional books, guitar magazines, etc, that is mostly a waste of money.
As I've matured a bit, I've re-remembered that tone is in your fingers (not your gear) and you improve only as you actually practice. Both of these realisations help you avoid the dread Gear Acquisition Syndrome that so plagues many guitarists. Remembering that practicing my vibrato will improve my tone more than would buying a Parker Mojo or Variax would helps me walk by the displays in the guitar store without stopping and motivates me to spend more time actually practicing.
Similiarly, remembering that I really need more hours on sweep picking or practicing across the neck CAGED licks helps me avoid the temptation to purchase the dvd that promises I too, in just 35 minutes, can sound just like Eddie, Jimi, or Stevie. Like most mediocre guitar players, I've really got more foundational stuff to practice than I have time or discipline to practice. The problem isn't knowing what to practice, it's just actually doing it.
That said, sometimes you just need to try something different to get out of a rut or to get back into practicing. Fortunately this is a lot easier to do now than it was just a few years ago.
<old codger voice>Back when I first started playing guitar and looking for resources online, I'd often find TABs of songs (remember when OLGA used to be good? Before the lawsuits?) Occasionally I'd find a lesson: tab or notation along with comments about how to play and what sort of technique is used. Very occasionally, if I was really lucky, I'd find a lesson with accompanying sounds (.rm or even .wav back in the day).</old codger voice>
That was then. Nowadays when I'm looking for internet guitar resources I demand at least PDF's with nice notation and accompanying sound samples. Ideally, there should be video samples as well (nothing like seeing the hands!) Lately I've been using the free guitar lessons with videos at freeguitarvideos.com. These are short but typically demonstrate one or two riffs, scales or techniques and are grouped by genre. Very good stuff. I'm working on the country style section to add a few different rhythm techniques to my arsenal. Also I've looked at some of the free lessons at the famous Berklee School of Music. Their site www.berkleeshares.com has a grab bag of lessons (many with video) for Guitar and Bass (also other intruments, vocal lessons, etc, but I haven't explored there as much). There's some pretty sophisticated stuff here (the Jazz Voicings for Guitar lesson, for instance). Finally I discovered the Fender Players Club at www.fenderplayersclub.com. It's got a lot of "in the Style of" lessons aimed at getting the aforementioned Jimi and Stevie sounds, but it also has some less predictable stuff (Dick Dale? Waylon Jennings?). See the whole list here. No video here, but most come with .mp3 tracks at least.
Did I miss your favorite free guitar lessons site? Hit my contact form and drop me an note and I'll put up worthy candidates...Update: Also found www.freelicks.net. A few too many ads, but a bunch of free videos. I also found Anthony Garone's site which has a few videos. Anthony had the brilliant idea of using google video to host his video which means he only has to pay for the bandwidth of the text on the page... Brilliant.