I learned about it in high school -- haven't thought about it since then. But I do know there was a major banking crisis just as things seemed to be recovering from the US stock market crash. Let me see what I can find.
Okay, there's something in Google Books at
http://books.google.com/books?id=pq1tB3BDeuwC&pg=PA259&lpg=PA259&dq=1930+europe+banking+crisis&source=web&ots=ou4ftbxQC2&sig=_ABpvGFtMkvMoenqIZKzl3Yh2Uw&hl=en&ei=bAObSe3OIoGCtweKr5WpCw&sa=X&oi=book_result&resnum=1&ct=result and more at
http://books.google.com/books?id=tXo6CAkhoroC&pg=PA134&lpg=PA134&dq=1930+europe+banking+crisis&source=web&ots=FJmd5X6zZ6&sig=UBCZEHPT-zumJWGLJEmfVazLL28&hl=en&ei=bAObSe3OIoGCtweKr5WpCw&sa=X&oi=book_result&resnum=4&ct=result#PPA136,M1Basically, there were banking crises in Austria in May 1930 and in Germany in June -- when is exactly when that 1929 graph goes south -- and "an international crisis of financial confidence in early July." The Bank of England was slow to respond because they didn't think that what happened in Germany could affect them, and England was actually benefiting from capital flight from Central Europe. (The crisis was also regarded by British policy-makers as a convenient opportunity to suspend German reparation payments, which were seen as financially destabilizing.)
Commodities prices also kept falling throughout 1930 -- and that in turn led to a decline in long-term lending -- which produced a deflationary feedback loop, where producers had to sell more at ever-lower prices because they could no longer borrow. The causes of the decline in lending are debatable -- and may have been more psychological than anything else -- but that decline, combined with the banking crisis, turned a modest recovery in the first half of 1930 into a renewed collapse by that fall.
Runs on banks reached the US in November of 1930, and by 1931 there was yet another financial crisis under way. By then, the British government was attempting to respond by cutting spending, particularly social spending on behalf of the poor and working class. And from there on, things just kept getting worse.