Since there hasn't been a posting to the Guestbook forum for over two years, I thought I'd use that as an excuse for publicising my own website devoted to unsolved problems, which can be found at
http://unsolvedproblems.org/ which lists many problems which may or may not be amenable to the problem-solving abilities of some here......
I figure one more plug for my website after a 3-year gap is not excessive, so....let me just point out that most puzzles on my site at http://unsolvedproblems.org/ now carry a prize of US$1,500 and a bottle of champagne....