In 2005, The Codex Sinaiticus Project was established by the four institutions holding pages of the codex for the purpose of research, conservation, digitization, transcription, and dissemination. A website gives the history of the manuscript and the latest activities of the Project. You can view the entire manuscript (while the New Testament is complete, only portions of the Septuagint Old Testament have survived) by clicking on “See the Manuscript” at the top of the page. Choose the passage or page you want to view just above the image of the codex.
Selected pages can also be seen at the British Library site.