Ignored Users Society.

-san
The suffix -san, such as "Smith-san" is a generic word for Mr./Mrs./Ms.
It implies some level of formality or distance between the speaker and the person referred to.

-sama
This is a much more polite term than "-san", and is reserved for people of a higher status. This status could be based on relationship (i.e. a store clerk and a customer)

-kun
This is a term generally reserved for males and those of a lesser standing.
It is also more "familiar" term, so it may be used as a term of endearment for a younger person within an organization.

-chan
This is a term generally reserved for younger females. It can denote a closer relationship between the speaker and the one referred to.

Onii-sama, Nii-san, Onii-san, Nii-chan, Ani, Aniki
These are all terms for "older brother". Depending on the suffix, it can be more or less formal.

Onee-sama, Nee-san, Onee-san, Nee-chan, Ane, Aneki
These are all terms for "older sister". As with the above, varying levels of formality.

Senpai
This is a term to refer to a senior in your organization. This could mean many things.
In a karate class, it could be someone of higher rank. In school, it could be an upperclassman.

Sensei
Sensei means literally "teacher", so it is a term reserved for... teachers. But it also can be used for people you respect greatly.