Exchange Invite Codes
You can use this tool to exchange your unused invite codes for a coupon which you can then use at the LiveJournal Store.
You will receive $0.50 for each of your first 10 invite codes, then $0.25 for each additional code, with a maximum of $25.00. Since you have a total of 55 unused invite codes, the final amount will be $16.25.
First go to http://www.livejournal.com/invite/gen.bml and then to http://www.livejournal.com/invite/claim.bml to claim your coupons.