my supervisor keeps forgetting our meetings... is this normal? How do you all deal with it? Should I have to put up with it?

No it's rubbish. At my Uni, I was given a resaerch students handbook when I started setting out guide lines to what to expect and what my 'rights' were to supervision, min ammount of hours per year etc.
How many times have they forgot?

It is anoying. Mine has done it a couple of times - usually double booking me with other students. I tend not to be too angry with her because I think it's in my best interests to keep good relations with her. I do find myself 'managing up' though, by which I mean I might e-mail her about something else the week before a supervision and drop in the date and time of the meeting in the e-mail to remind her just in case! even if it's just 'see you Tuesday at 1pm'. lol!

I don't think we should have to put up with it, and it does make your work feel less important. But personally I wouldn't want to fall out over it as my supervisor is v. supportive in other ways, and I try to remember she is human too, a busy academic and makes mistakes. If she was less supportive overal I think I would take tougher action.