How do I investigate an address or transaction?
The simplest way to get information about the transaction is to use the Blockchain web site.  They have some easy-use-tools that can show you which transactions the funds came from, and the submitting IP address.  Use the URL http://blockchain.info/tx/transactionid.

For example: http://blockchain.info/tx/cc4ffa39d766fadfc6bd48a2144492e6e7b07c9b4046f7edbad3ec63869dd071

I don't think you'll get much information about the IP address, because addresses are not part of the transaction information.  A Bitcoin host only knows the address of the peer that relayed a transaction, which usually isn't the originating address.

You can trace what other transactions your donation came from, but putting a name to a bitcoin address can be difficult.  Your best bet might be to do a Google search for the address of some of the upstream transactions.  If someone used their well-known address for donating, then you might be able to find them.  But if the originating addresses were never put onto a web page by their owners, then you're out of luck.

If you are a government and the funds originated through one of the currency exchanges, you could use a warrant to get whatever information the exchange has on a transaction.  Given the state of privacy rights these days... well don't get me started.