Paul Graham at Y Combinator posts an interesting list of "Startup Ideas We'd Like to Fund".
My favorites are Fix Advertising, Fixing E-mail Overload, and New News.
Found via John Cook, who notes that many are working on most of these ideas, but "ideas are a dime a dozen [and] it all comes down to execution." Can't argue with that.
Please see also "What to advertise when there is no commercial intent?", "Attention and Life Hacking", and Findory.