Where can I buy stickers/labels to put on rack systems/servers to identify them? I want to put my companies logo on them and also I want 2 sizes: small and larger. The larger stickers should have a place to write the IP Address on them and/or the system name.
Sysadmins typically use P-Touch labelers to identify servers by name and IP address. It is best to use a PC-connectable model with an ample supply of white-on-black TZ tape. Note that the "default" label tape color is black-on-white, which is more likely to look unattractive or unprofessional on a black server chassis.
As for stickers with your company logo, you may want to look at getting asset tags which include not only your company name or logo but also a serial number. Both accounting people and security auditors generally smile upon the use of asset tags (example), especially when the tag numbers have been entered into an asset-tracking database like OCS Inventory NG.
Talk to any company that sells stickers or labels. Google is your friend.
You'll find that most shops use some variant of a dymo label maker, and dispense with the logo bit.
I'd just pick up some of these and design and print them yourself.
That said, I've never seen a company that had their logo printed on the server/rack labels - often there's very little space available on the front panel of most servers, making it difficult to apply anything but a small label with hostname.
Additionally - you really don't want to hand-write these labels - that's just asking for problems. As voretaq7 suggested, pick up a label printer and be done with it.