I really think I should share with everyone a good source of rebates I've found. PriceGrabber.com is an online cost comparison tool with reviews built in. It's been around, but I only really started using it after TomsHardware.com linked it in with their TG Stores system.
Well, the great thing about it besides reviews and clear-cut cost comparison is that they offer $5 bonus rebates on select items. Typically, if something is new, hot, or expensive they will put the $5 bonus up to get people to review the item. I did this for my OCZ 2GB RAM kit and I got the check back in only 5 weeks (quite a record for MIRs).
You can do this not only for recently ordered items, but for items you bought months ago. I did another rebate for a Seasonic S12-430W PSU I got last July, and another one for my LianLi V1000A Plus case. I checked back again, and they added one for my Zalman CNPS 7000B-CU LED CPU HSF.
It limits you to 5 rebates per month I think, to prevent abuse. You can also pre-emptively request a rebate for something you haven't ordered yet, but might, and then you just have 3-4 months before you must postmark it. You will want to do this because they only provide the rebate form to the first 50 people who request it. These forms aren't exactly flying off the site either, which is good. I'm still picking up rebate forms for stuff I got in July (3, as I mentioned).
The submission requirements are typical and you will need to photocopy the UPC and receipt/invoice. I keep all my boxes so I don't have any trouble with that, I even keep photocopies of UPCs I mailed for other MIRs. The last requirement is that you post a review on the site for the item, which is the whole purpose behind these rebates (and maybe to get manufacturer compensation).