Back when I worked a day job, I spent a lot of time importing gadgets and toys from China and other parts of Asia. It's a massive headache in most cases, but it's definitely amazing how cheap things are if you buy them directly.
If you're not ready to commit to 3000+ units (sometimes 10,000+ or even 100,000+ depending on the company and item), check out Brando (shop.brando.com.hk) and USBGeek.com. They don't carry everything, but the selection is decent and they'll give you about half off the US retail. You may need to contact them directly for the bulk pricing. You can definitely do better on your own, but importing thousands of an item can get a little insane, so this may be a decent alternative depending on your situation.
Like a lot of other people said, Alibaba is a good site, but definitely full of scams. Before you send someone money, make sure you check both Google and the Alibaba forums to find out about the company you're dealing with. People there can give you a lot of detailed advice on scam avoidance. Remember that most large orders will require wire payment, so the odds of getting your money back are not good.
A couple of other notes:
-Make sure you know their defective policy before buying. Depending on the item and factory, I've seen defective rates as high as 10%, and that can definitely cut into your profits. Some companies require you to ship back defectives, others require photos, some go on your word, etc.
-Get precise shipping quotes up front. NEVER just hand over your UPS # and tell them to send it over. Even with good shipping, you'll probably pay $.50-$3+ per item to get the products over here. Most of the international shipments will be calculated on dimensional weight, which takes into account both weight and size. Get familiar with it and start figuring out whether you're looking at a container load, LCL (less than a container load), or just a couple of boxes sent over by UPS. In many cases, it may be worthwhile to look into freight forwarders, but UPS has dramatically improved their options from China/Hong Kong, so I'd start there first.
-If you can't find the item you're looking for, brainstorm odd phrases people could use to describe the item. Sometimes, Chinese factories want to hide the fact that they're copying a certain product - or they just don't know what to call an item - so they say really strange things. I remember looking for a USB Plasma Ball a couple of years ago and the only supplier listed at the time was calling it a "Super Happy Glow Ball USB". Often, stripping a product search to just one or two essential words will help you bring up better results (as in the case before, where USB Plasma Ball brought up nothing and USB Ball got results).
-Check promotional products companies in the US. Although they won't give you direct-from-China rates, you can occasionally negotiate a great discount with far less headache, especially if you make it clear that you don't want the items imprinted.
-Get a sample before committing. Even if you've seen the item before elsewhere and you know it's good, get a sample from the company you'll be working with. I had one situation where I was ordering a specific salt and pepper shaker set from a US company that manufacturer in Thailand and I wanted to find a better deal from an Asian manufacturer. We found one company in Hong Kong that offered the item at $2.00 each (80% less than what we were paying from the US), so I ordered a sample. The holes for the salt and pepper were so large that salt just poured in a steady stream onto the food. I was mad that it ruined my lunch (should have tested it elsewhere), but it was better than ending up with 10,000 of them. The company was unwilling to address the quality issue, so we moved on.
-Pour yourself a drink before you sit down to research. Chinese factory pages take forever to load.
