Buying Stuff
It's always a surprise to me when I meet people with Internet access who, when buying stuff, choose to pay much more for an item than they need to. Often they pay hundreds of pounds more.
As an example, only four months ago I wanted a new High Definition TV. I first went to Comet and Currys to see what was on offer, looked tha the specifications, and made a list of manufacturers and models. I wanted a 40 nch high definition with a resolution of 1080p (the highest HD spec). I liked the look of the Samsung LE40M86BD. I was able to view the specification on the excellent review site here. The independent review of the model I had chosed can be seen here. The Comet in-store price at that time for this model was £1399, and Comet's on-line price for store pick-up was £1299. I then went here, and here to find the lowest price at £790 with £40 (next-day) delivery, making a total cost of £830. This saved me £469 (or £569 for the in-store price).
These two sites are probably the best for finding almost any consumer goods and the lowest price. I have previously saved myself £200 on a top-of-the-range washing machine, £70 on a hard-disk/DVD recorder, and £40 on a DVD player that supports all formats (including DivX).
In additon to the higher-value items things like high-quality HDMI cables can be purchased at a fraction of the in-store prices. The guy in the shop, though, will assert that "you can't by the same quality at a lower price on-line" - but he's going to say this isn't he? If he were to acknowledge that there are cheaper options on-line then he's at best losing some of his bonus - at worst in danger of losing his job.