I had a little fling with flyers, around the time of the massive stop the war demo a year or two ago.
I thought 'charity site, militant people - worth a go?' and printed off several thousand to distribute and got my mates to help. I overwhelmingly found that people would throw them back in my face 'this is a peace demo, not an advertising op!' without looking at them or seeing that it was for charity, not just for my benefit.
While i did get many people to accept them I saw no noticable rise in traffic and as I only keep 8% of the commissions I recieve to cover costs they in no way proved to be an effective form of advertising.
Experience in major shopping centres etc may differ - and I'm sure you can always pay some students £5/hr to dish them out for you. Look for towns with a healthy nightlife for cheap flyer production rates.
I also asked local shops to put them up in windows etc but as there is no way of tracking the results of such a promotion it's impossible to tell whether people then came and had a look or (as I suspect) thought 'ooh that's a nice idea' and promptly forgot all about it.
I've always meant to spend more time getting
PR, building up a brand etc and now I'm suffering for it - c'est la vie..