First off you have to give eBay a visit. On eBay you can find a vast variety of magic tricks some new, some used. You can pickup books, eBooks, illusions and professional magic tricks, many for ridiculously low prices. (The following items are ending soon!)
Maybe you want magic and you want it now! Well have you visited PubTricks.com before? They have literally hundreds of tricks you can watch for free, then if you like any effects you purchase the download video tutorial. PubTricks.com always have a Free Trick Thursday!
Here are some of my personal favourite effects from PubTricks:
Now if you insist on hard tangible goods and gimmicks in the post for a more traditional shopping experience you can't beat a good online magic shop.
I throughly recommend eMagic Supply. They have literally hundreds of fantastic effects ranging from street magic to cards, coins, mentalism, pub tricks and general magic. The fantastic prices, great tricks and fast shipping is why I have used them for many years.
You might also like to check out International Magic if you don't find what you're looking for at the other stores or just to compare prices. International Magic offer a vast variety of effects, great service and best of all if you are in the area you can't beat visiting their London store (I prefer it to their website!). I have literally spent thousands in that store, Martin and the team always have time for you!
Together, these sites pretty much cover all your magic needs for those magical performances. Happy conjuring!