Let me see, I've bought a BUNCH of stuff online over the last few years...
I've bought off eBay, and with eBay, some categories have been outstanding, some categories have been absolute crap.
There's
no way in hell I'll buy computer gear on eBay any more.
I bought an AthlonXP 2400+ processor & ECS Motherboard off a dude (Ok, so ECS makes crappy boards, but it was a super deal, and the combo was still cheaper than buying just the chip alone from Best Buy)...
All was running sweet for about 2 months (30 day warranty on the hardware)... Then, the motherboard took out the CPU, my CD-Burner (that I'd only had for a year), and the processor.
I bought a fan from a company on eBay with a 10000 rating. It took me 3 weeks after payment to receive the fan and when it got here it was broken. I sent it back and it took another 6 weeks to get a replacement fan.
I've bought various other things on eBay that are computer related and all have turned out bad except for the USB2 CompactFlash reader that the UPS guy dropped off for me this afternoon. It crashed the PC a couple of times during installation (which is no simple task under Win2K, heh), but now it's working sweet, and very fast, and for 12 bucks shipped, I certainly ain't complaining.
I have also bought camera equipment off eBay. I've bought film, I've bought some top notch SLR Lenses, and they've all been exactly or BETTER than described, and I have NO problem buying photo gear on eBay (even though the photo area does have some bad sellers, you learn to spot the ads to avoid pretty quickly).
I've bought "Magic The Gathering" cards on eBay for my girlfriend's son (I must've spent over 400 bucks on those for him over the last couple of years on eBay). Every single one of those deals (and there were about 90 deals in all) went smooth.
So, aside from computer gear, I'm pretty satisfied with eBay.
I've also bought second hand from other online communities. My Nikon N90s 35mm SLR camera, and my MF-26 databack came from a guy on Nikonians.com. Another GREAT group of people, VERY helpful, just like the community here. This camera looked like it'd just come straight from the factory, it was in SUPREME condition, and my total cost, including shipping, was about half of the retail value of the equipment. In fact, I just sent him a bunch of money a coupla days ago for a Nikon 28-80 AF lens, and I will be buying his 70-300 AF lens when he upgrades to the VR model. VERY nice people, all of them, and very protective of their cameras, so I know anything I buy from them will be in great condition, and if it's not, they say so in the ad! and exactly how the not-great-condition affects functionality (if at all - many times it's just minor cosmetic scratches).
As far as brand new from stores goes... I've bought computer gear from NewEgg.com, never had a problem, I've bought feeders for our reptiles from Armstrong's Crickets, ReptileFood.com, and several other companies - although Armstrong's & ReptileFood.com are the only ones we'll order bugs online from now.
We've also spent a couple of grand on supplies for our reptiles at reptiledirect.com - and never had a problem with them 'cept the high shipping rates, heh.
I've also bought online from breeders (snakes, beardies, leopard geckos), although due to the problems with some shipping companies (mostly FedEx & UPS), I don't like to ship live animals (unless they're shipped with Airborne Express who do a pretty good job). So, usually I will pick my animal online, pay via PayPal, then pick up at a local show (here in Sarasota, there's shows within a 2-3hr driving distance every 3 months or so, including the largest reptile show in the world at Daytona every august - which is an absolutely EXTREME weekend, probably the highlight of the year, the most amazing LARGE group of people you're ever likely to meet offline).
Oh, for those of you in the UK, last time I was there, I bought a gig of RAM from novatech.co.uk, absolutely great people, extremely fast shipping, great prices.
That's all I can remember off-hand
