There are several ancient Greek New Testaments available and one Hebrew Old Testament. The Greek New Testaments are listed under the “GREEK (GRC) – Κοινη” entry in the list of available Bibles here: http://www.biblegateway.com/versions/. Currently there are four ancient Greek New Testaments available:
- SBL Greek New Testament
- 1550 Stephanus New Testament
- 1881 Westcott-Hort New Testament
- 1894 Scrivener New Testament
The Hebrew Old Testament that is available is the Westminster Leningrad Codex, listed in the HEBREW (HE) – תירביע section in our list of available Bibles. You can see it here: http://www.biblegateway.com/versions/index.php?action=getVersionInfo&vid=81.
You can search or look up passages in the Greek or Hebrew text like you would with any other Bible.