The Septuagint is a rich resource for those studying the Old Testament. For many of the writers of the New Testament, the LXX was the preferred translation (for example, that is all the author of Hebrews uses in his Old Testament quotations). The problem for the modern minister, who perhaps isn’t as sharp in Greek as he would like to be, is in finding a reliable translation. Back in 2007 the New English Translation of the Septuagint (NETS) was published and is available for free online. While I am not always thrilled with its renderings, it is nevertheless a valuable resource when studying an Old Testament passage—even more so when studying a New Testament passage that quotes the Old Testament. In most instances, our modern English Bibles follow the Masoretic Text for the Old Testament (for good reason, I would add). But having a reliable text for comparison is essential for in-depth study. Enjoy!
Visit the NETS site, where you can view the text online for free.
As an added bonus, there are a few excellent interlinear versions available online. Each of the following sites also offers the full text for free online.
Hebrew-English Interlinear (Leningrad Codex w/ vowel markings)
Septuagint Greek-English Interlinear (this appears to be an eclectic text)
For those not familiar with the Septuagint (or rather, the “Septuagints” plural—for there are several versions), a handy printed resource is a book called The Invitation to the Septuagint by Karen Jobes (published by Baker).