Here's how I make good passwords:
Pick a short keyword that's easy to type -- say, 'left'. Replace some letters with numbers (l3ft) and, for good measure, capitalize some stuff (l3Ft). Now, every time you need to make a password for something, take the name of the thing and stick your keyword on to it somewhere: l3Ftgmail.
This part is fairly well-known (although, still, not enough people use it!!!). What's fun is to make like a linguist and treat your keyword as a real affix. You can affix it anywhere to the name of whatever you need a password for, not just at the beginning or end (prefix or suffix). You can also infix it (gl3Ftmail or gmail3Ftl), or circumfix it (l3gmailFt).
This method doesn't completely specify your password. Sometimes you need to use an acronym for the service instead of the full name (su, or supon, for StumbleUpon), to keep the password from being too long. And sometimes I can't remember whether my YouTube password uses yt, ytube, or youtube. But it doesn't matter, because there are only a few possibilities I need to guess. What's more, this makes it easy to change passwords and still remember them fairly easily -- just move your keyword from prefix to suffix to circumfix to infix...