Virtually anything, because I have a knack for looking at things at multiple perspectives and analyzing, and creating interest out of nothing. At least, for myself, I don't think I can make the dullest thing interesting to everybody.
The things that stimulate me most are areas of interest, music, conflict (

), peace (yeah I know, way to be indecisive, but peace
ismy preferred style), happy, quality time spent with other people, principles and ideas, occasional solitude, talking (unless I don't like somebody), exploring, and doing things (it makes use of the energy that's rapidly going to my mind.)
Life offers so much...
How much external stimulation can you tolerate?
I can take a lot of it, it's not even a big deal to me and for me it's not related to my introversion; it's about whether or not I find anything enjoyable about the...stimulation. If I like being stimulated...:rolli:
For instance, there's this "friend" I have who is insanely loud and "worships me." Sometimes he just goes up to my face and says "HEY (name)!" Then my face immediately goes to my "unimpressed" look, and I get irritated, yet I greet him back, because he isn't a
bad person and it's not a severe violation of any of my principles to say hi to someone who I dislike (and to me, this means that something is "not a big deal." It would be obvious to anyone but this guy that I don't think too highly of him.)
At concerts, if the crowd and the band are going ballistic but I hate the music then I shut out the external world. But if I like the music, and I feel energetic, then I get into it too, sometimes. I have mixed feelings on moshing, though.
Flashing colors can be very exciting to me, but I like colors. It all comes down to my judgments on whatever the stimuli is.
I'm somewhat flexible...
What is your internal world like?
I don't know how to explain it...it's pretty much filled with EVERYTHING I've ever known: people, events, music, outer space, video games, nature, animals, projects, deadlines, feelings, thoughts, books, objects, problems, worries, what I see at a given moment, things concrete and abstract. It's the same thing as "my external world" but on the inside to me things feel more cohesive and related, offering a sense of calm. The external world, though full of "things" (and I love it for that), seems chaotic at times, and my "internal world" remembers these things. So the inside lets me process if I can't immediately "handle" something that's just happened.
My internal world...is not a fantasy world, or the fantasy version of the external world. Sure, I have fantasies and stuff, but it's not like my inside is a distortion of the outside, it's more of a copy of the outside that is personal (but not strictly private.) It's a copy (not a fake) that I feel truly belongs to me, it's like a journal (which I have). It is organized, but sometimes I ignore the categories of things in my insides and everything will smear together. This isn't really a big deal though. And the way I define things inside is really arbitrary, but usually I associate things with memories, feelings, or interests, and it all fits into a timeline.
It sounds complex, but it's not.
How much alone time do you need and how often do you need it?
This is much like the external stimuli thing. How much alone time I need is influenced by the things that happen in a given amount of time. If something happens to me that really sucks, then my first instinct is going to be to turn to myself and ruminate, even though I know going to other people is a good idea. If something happens to me that is really good, then my first instinct is going to be turn to myself and try to "handle" the good thing that happened. I have a high threshold for crap happening to me or things that I dislike, so it typically doesn't make me need more alone time, but when something good happens to me then I need more alone time.
Alone time is the time for really hardcore processing of things though. This is when I'm dealing with something important or a lot of things at once. My mind works twice as hard as it usually does then. Alone time is something of a necessity for me...as it is for everybody I'm sure, but I value it more than a lot of extroverts, I'd bet. If I
reallyneeded that alone time and someone bursts that bubble then I'll usually get irritated.
I hate making things sound like a bigger deal than they are, because I can and often "process" things in the presence of other people without being weird about it (I'm not usually very weird about it anyway). I need alone time every day, but I don't have to actually be alone to have it--when I shut out everything around me, and I'm REALLY spacing out, then that's alone time. If I look spaced out and I'm interrupted, but I don't seem irritated, you just caught me being naturally thoughtful or calm. If I REALLY need alone time I go out of my way to avoid people anyway, but I never need that much.
What comes along with being an introvert that most people don't realize?
Well,
-That it's not a big deal. Introversion does not mean antisocial.
-That it's not a big deal. Introversion does not mean mystic/cool/quiet/shy.
Personally, I don't feel bored or lonely often, but I'm a human being first and an introvert second, and I need to hang around people too. Being an introvert can tell a lot about a person, but it's not something that's supposed to dominate someone's thinking when approaching people. There are billions of kinds of introverts, silly ones, serious ones, stupid ones, slippery ones, and something else that begins with an s. The stereotypes are true only to an extent.
That being said, I have been shy, quiet, and awkward for a long time, and I worked hard to get out of that. I used to be really rude, overbearing, and tactless. Sometimes, I end up overcompensating, like for example, I have gotten this idea into my head somehow that whenever I make eye contact with somebody...anybody, I'm supposed to greet them, for the sake of good manners. I've been curbing that for a while. It's been like an annoying habit, like biting your nails. Sometimes I make more attempts at conversation than necessary, too, out of worry that I'm making someone else feel too uncomfortable (extrovert or introvert.) I'll say really stupid things just for the sake of talking, when I don't really want to. I'm just getting used to caring a bit more, but I'm a lot better with finding that middle ground nowadays.
So I'm a friendly guy, and I don't want to say I put up fronts, but I can't help but say that I don't do everything naturally...which makes me kind of ashamed, but that's a personal thing.
In any case, introversion is just a facet of who I am.
Edit: Awesome, I wrote an essay... T_T
Edit again: What's with the anti-small talk sentiment? If you want to "find out" things about a person, small talk can do just that, by revealing things like interests and opinions on small things. This offers insight into character. But why not talking for it's own sake?
Edit again and again: Introversion, as with any personality trait, excuses NOTHING about a person. Some people never grow up because they let that be who they are. INTJ's for example, yeah, "INTJ's needs a lot of time alone to think and process blah blah blah blah," true as that may be, it doesn't give them (or anyone) the right to be unfair in their introversion (calling friends every three months, etc.)