None of them is great, but the point is that every one of 'em (well, all the ones I've read) could be, if executed correctly, a perfectly viable business. Picking out a few at random:

Presentation Consulting - Teach companies how to improve their presentations

That's not a bad idea. Is somebody already doing it? Possibly, but that doesn't mean you can't do it too.

Online flower shop with one-hour delivery

Sounds tricky, and you'd need to restrict it to a couple of major and dense cities, but again there's no reason it's not a viable business. Market it correctly by encouraging men to send their ladies flowers spontaneously, and you could surely make some money.

Build Your Own Back Pack Shop

Damn you, random numbers! I don't much like this idea, but there's gotta be somebody out there (schoolkids, I guess) who would love to build customized backpacks for themselves. Great idea? No. World changing? No. Profitable if you get the product and the marketing right? Sure!