While I still consider myself a pretty 'basic' stitcher, upon closer inspection, there are quite a few things I use - most of them I have picked up during the last year of following the online stitching community :D I'm not going to list basic stuff like fabric, scissors, needles or floss here, as I don't really consider those 'gadgets'.
So let's see - one thing really important to me is using working copies of my patterns and a pair of markers. I use yellow to mark the stitches I'm doing next (like, everything in one color in a certain area), then go over that with orange once the stitches are done. Makes navigating confetti heavy patterns so much easier! I still get the occasional "missed one more stitch", but it's much better than before.
In the same direction, I recently started to use magic guide line (it's really just red overpriced fishing line but I couldn't get anything else around here) to grid my fabric. I'm not doing this for every project, especially not for smaller ones, but for full coverage designs and/or working on evenweave fabric, it does help a lot!
One thing I started while working on a Teresa Wentzler design (lots of combined threads if you don't know those) was pre threading several needles with different colours to make switching easier. I just stuck the needles into a piece of paper and marked them with the corresponding symbols, but now for Dark Force I got a Pako Needle organizer - it has little holes with a spongy stuff to put the needles in, and replaceable cards to put the symbols on. Again, I won't do this for every project, but I'm thinking of getting a few more of those to use on projects that switch colours a lot :)
What I also use (and love) are daylight lamps - I got two different ones, one that stands behind the couch and a small one I can take with me when I travel, and I'll buy another one for my desk sometime soon. The light really does do wonders on how good you see things and how tired your eyes get, if you can't stitch in natural daylight, it's the next best thing!
As for frames, I prefer my q snaps - I like how they are rectangular rather than round, which allows them to be places closer to the corner of a design, and I think they can get the fabric pretty nice and tense without hurting the stitches to much when being places on top of them. I haven't quite gotten the hang of scroll frames yet. although I have one and might try to get it right again some time. I'm not sure about floor/lap stands yet, sure, two-handed stitching is faster, but I don't know, it looks really uncomfortable to me...
I also have a needle minder a friend gave to me. I love it, but mostly for decorative purposes - I don't think it's all that useful, but pretty it is! :)