Therian: I can't really say to much because I consider myself a Therian bit hypocritical if I poked fun at myself lol, but onto all seriousness. The definition of a therian changes drastically from person to person as it is up to each person to come to there own opinions and conclusions of what a Therian is. Events such as "shifts" are when someone becomes more in touch with there animal side, there are a few general categories of shifts, Physical, Dream, Sensory(Often Not Considered A Shifting), Phantom, Mental, and Cameo. Though Physical shifts are imposable there still included in the list of categories personally I don't know why they even have it then, next is Dream which very loosely defined as it can be any therianthropic related event inside of a dream, next is Sensory which is basically a heightening of your senses, next Phantom simply meaning Phantom Limbs of your theriotype, Metal which is pretty self explanatory, normally consisting of the person blacking out and then having the metal state of said animal, Cameo shifting is when you have any of the above shifts, except as an animal other than your theriotype. So in a nut shell a therian is just anyone who thinks they or has a strong connection with an animal (don't shoot me if you don't like that nutshell definition of a therian its just what to Wikipedia said.)
Other-kin: Basically the same definition of a therian, except instead of being an animal... your a mythological creature, elven, angelic, demonic, Draconic, etc. etc. etc. Personally I can understand therianthropy because its based around the belief of being a real documented animal, but I don't throw the Other-kin community to much of a bone because thats like saying your theriotype is a rock, or a wooden chair. I understand nobody can possible understand the mental state of a different animal because its imposable, and all we can go on is speculation of how we think they think based on there actions... but when something has no proof of ever existing. How can you say you feel like it? thats my biggest problem with the other-kin community. But to be fair I've never been very far into the other-kin communities either, the farthest I ever went into it was just curiously poking at random forums and wiki's.
The Vampire Community: I have a few friends who consider themselves "vampires" so I'll keep my personal opinions to my self so I don't offend anyone. But the community original started along with the other two around 1992 on a message board which I can't remember the name of nor do I care enough to go look it up. But since Grarulfr did a good Job laying out basically what a modern day vampire is I'll just quote him. >.>
Written by Grarulfr earlier on in the thread
Now we get into these two main types I mentioned (http://www.thefurryforum.com/forums/Smileys/Fox/grin.gif)
Sanguarian
A sang...well, to simply put this, they crave blood. When they need to "feed" they are hit by these blood cravings, perhaps having disturbing thought patterns such as wanting to attack someone for their blood, seeing just a little could set their mouth watering etc. you get the idea, though it's a very rare case that they will actually go through with harming someone for their blood though there is increased agression, being edgy, snappy, the thought of the stuff in their mind throughout the day, all day until they feed. Mentioning feeding you can forget the typical image of climbing through a window and biting into someones neck in the dead of night, the sang generally finds a donor, someone willing to cut or be cut for the sang to drink from them (not much however is needed, again, forget the myth), it takes part in a controlled environment with sterile equipment and knowing how to perform it (so no going for the neck people) and blood tests have been taken to ensure that nothing like AIDS can be transferred to the unfortuneate sang, of course this isn't always the case so the smart vampire will take the extra precautions to avoid harming the donor or themself, or they of course just Psi feed (http://www.thefurryforum.com/forums/Smileys/Fox/tongue.gif)
Psi
A Psi is different in the ways of the sang as you can tell them apart pretty easily - a Psi doesn't have blood cravings yet they still have the need to feed. A psi feeds, well. they don't even need to touch a person, more of taking the energy remotely (this includes over the internet - long story but a connection is involved) they take energy from a persons aura and as they have been feeding they typically feel energised or stronger, some report a complete and utter lack of being able to concentrate and this is generally a sign to feed. In turn this can be done by taking from someone willing to donate, from a group of people to take as little as possible from a person yet still be satisfied. Though of course you get the bad kind...the kind that attack people for their energy, draining them leaving them in pain and pretty much...well, drained. I assure you though, someone attacking you might be able to hurt you but you can't be killed, your body would need to build up your energy levels again is all. Though if you know the protection methods such as closing chakras and shielding you should be good to go (http://www.thefurryforum.com/forums/Smileys/Fox/wink.gif)