It's a great quote and all, and very true. I'm not trying to be annoying but I've seen this repeated thousands of times but it's apparently not from Albert.
Albert Einstein quotes: Misattributed
The definition of insanity is doing the same thing over and over and expecting different results.
Variously misattributed to figures also including Benjamin Franklin and Mark Twain. The earliest known occurrence, and probable origin, is from a 1981 text from Narcotics Anonymous.
http://en.wikiquote.org/wiki/Albert_Einstein#Misattributed
Wikiquotes has been very accurate in the past, maybe they're wrong here but I doubt it. Many quotation pages are simply wrong, if Wikiquotes is right. It's repeated so often that it has become fact.
Again according to Wikiquote it was a woman named Rita Mae Brown who quoted it from a Narcotics anon book and made it popular
Insanity is doing the same thing over and over again but expecting different results.
Brown did include this quote in her book Sudden Death (Bantam Books, New York, 1983), p. 68, but it appears she was just paraphrasing a quote that had already been written elsewhere. The earliest known appearance of a similar quote is the "approval version" of the Narcotics Anonymous "Basic Text" released in November 1981, which included the quote "Insanity is repeating the same mistakes and expecting different results." A PDF scan of the 1981 approval version can be found here, with the quote appearing on p. 11 (p. 25 of the PDF), at the end of the fourth paragraph (which begins "We have a disease; progressive, incurable and fatal"
.
http://en.wikiquote.org/wiki/Rita_Mae_Brown
Just for what it's worth.