Not sure what your budget is, or what you are selling...
But...
You can never go wrong giving away "keychain usb drives", or just a keychain logo of your business. (Preload a mini version of your product on the USB stick, setup an auto-run to load the "readme.htm" file, or something like that. Something they can delete, unless you want to force yourself on them, with a boot-loader to the file. That is how usb-programs hijack computers, just by plugging-in the USB. I hate those things... but if you just have it display a mini-webpage of your product, then that is not as intrusive, as they can just delete it from the stick.)
In bulk, you can get them for about $1-$3, shipped, as 2-8GB models. (The mini-usb or thin-usb are best for that.)
What would these "free items" be shipping with?
Other "generic" ideas...
- logo Pens (Everyone need another pen.)
- logo mousepad (non-intrusive corner logo, where it won't get "dirty" and will always be seen. Since you know they are on the internet...)
- credit-card USB memory (As opposed to a traditional usb, or keychain logo... more printing space, easier to put in a wallet/purse and not loose.)
- offline Credit voucher... (Offline, because it is a cold gesture... you expect them to actually loose it, but "remember" that they got it. lol, like most gift-cards others sell.)
- a rock... (Everybody wants a rock to wind a piece of string around... Don't they?
http://www.youtube.com/watch?v=amUowhHVBM4 )
- a ruler... (Everybody wants to rule the world... Had to put it too!
http://www.youtube.com/watch?v=ST86JM1RPl0 )