Does Ripple allow one to issue their own currency, similar to how ripples (XRP) were created at the system's inception?
Currently, only three-letter currencies that exist as IOUs can be created as a custom currency. And if someone else uses that same three-letter identifier for something else, each account can only transact in one of those conflicting currencies. So you could use "XBR" to mean people owe each other beers and you could use the ripple system to track how many beers you owe people or they owe you. You could accept payment in beers.
There are plans to introduce more customized currencies. There are some things you can't do without some specialization. For example, charging a storage fee as some gold storage agents would like to do. This is still in the design stages.
You can, of course, create IOUs denominated in any currency, subject only the what other people are willing to take. But if you want to create two accounts and have one owe the other $1,000,000, you can.