I try to spend a half hour or so a day playing around with Bill Handley's Speed Mathematics book (http://amzn.to/cE5hDu http://amzn.to/cE5hDu) The techniques a

I try to spend a half hour or so a day playing around with Bill Handley's Speed Mathematics book (http://amzn.to/cE5hDu http://amzn.to/cE5hDu) The techniques aren't quite as homespun as chunking/gridding, but they're definitely fun.