"Or something" is a phrase that appears to have entered the English language from the American quarter, illustrating for me that modern evolution of the language is not always duplicitous. It is a rather self-conscious phrase, originally only in spoken English, appended to a sentence where the speaker realises he has said something completely non sequitur and out of context. Its predominance in spoken English is because this realisation typically only occurs under the critical gaze of an audience.
It has also begun to enter informal written English, in similar context. Many online humour sites use this phrase after an extended off-topic outburst. I think it works quite well, hopefully indicating that the author is not, in fact, a moron with an eight second attention span, but is simply digressing for comic effect. However, like so many vernacular phrases, it should be avoided in any formal document, although perhaps you should not be aiming for the amusement of the reader in such situations anyway.
Example: "Well I'll be shaving my banana. Or something."
Also available for the discerning speaker is the subtle difference in "Or something?" The question mark or raised intonation implies that, although the preceding remark was in context, it was probably inappropriate. It conveys a certain embarrassment on the part of the speaker, and so is usually spoken slowly and accompanied by foot shuffling or other distraction techniques.
Example: "So, we could go and get coffee... or something?"