If you backed your paid apps up to iTunes all you have to do is sync them to your phone. If you didn't backup you'll have to call apple customer service to get them back. It's difficult, but if you stay on the phone with them, they'll let you re-download apps you've purchased. It helps if you kept your receipts for iTunes purchases. So you can forward them to apple customer service.
Wait for iCloud and you should be able to re-download all of your purchased apps. However, there has been a couple of bugs with that because someone got charged 121 times for Lion. So it's a bit of a flip coin. Otherwise, it looks like your only option is to contact Apple Customer Service because they should have a record of your transactions on your ID. I had the problem too and they fixed it for me the next day.