I use this website: http://www.breviary.net/
Published by the Confraternity of Ss. Peter and Paul. It is the old Breviary reformed by Saint Pope Pius X. Membership (IIRC) is $24.00 per year.
The Byzantine Divine Office is easier to use than the traditional or modern Roman offices because it has less variable parts than the Roman does.
The Eastern Orthodox and Byzantine Catholics have the same liturgical books with the only difference being that we pray for the Pope of Rome.
http://orthodox.seasidehosting.st/