At the end of the last episode of Cowboy Bebop, Spike collapses. It's not clear, but it looks as though he may be dead. Is there a way to know whether he is alive or dead (something in the background, comments from the director, a continuation in the story in the manga, etc.)
According to Wikipedia:
However, in an interview, Watanabe stated, “I’ve never officially said that he died. At this point, I can tell you that I’m not sure if he’s alive or dead.”
The link to the source is here. Though it's very hard to look at it, unfortunately.
In this more recent interview to Shinichiro Watanabe by Red Carpet News TV on MCM London Comic Con 2013, around minute 8 he says:
I've never actually said whether he is alive or dead in that final scene. That's up to the person watching to decide. I think that people who watch that and think that Spike is asleep are probably right. Just sleeping.
Although he still leaves the matter up to the viewer's interpretation, he seems to suggest that he is more likely to be alive.
Later on on the interview he also states that Spike is his favourite character, but then again, that does not mean he can't die at the end.
Shinichiro Watanabe has stated:
I've never officially said that he died. At this point, I can tell you that I’m not sure if he’s alive or dead
He decided to leave it open-ended, so, even with the many hypothesis on the internet, I guess the real answer is to ask yourself.
Source is the same as in Rapptz's answer: http://mrsspooky.net/bebop/TheDailyTexan.pdf at the top of page 5.