SpreadBit: Yes it is possible to create addresses and use them.
For example the address "12345678kQEmyaAoiQNYfam33WXfmpMSp1" can be used if you have the private key "5KGqWmamaD3rEbSmv1HY3CGyTnczjiBL9QhUKGtzXN29bKnMCFE"
You import address in bitcoin qt core software by typing at debug console:
importprivkey 5KGqWmamaD3rEbSmv1HY3CGyTnczjiBL9QhUKGtzXN29bKnMCFE
When "the message" in address is short it is easy to have private key, when generating address with long message =27 or =28 characters the private key could not be used - the address is usefull ony for sending bitcoins (and using message that way), but cannot be used for receiving bitcoins.