February 8 was International Septuagint Day, and I missed it. I'd put it in my diary for next year, except I haven't yet got a diary for next year. Dang!
This signficant commemoration only began in 2008 when the IOSCS (International Organisation for Septuagint and Cognate Studies) set aside the date "to promote the discipline." The IOSCS is the body that publishes the very useful NETS (New English Translation of the Septuagint) which is available online. For those profligates like myself who hastily invested in a hard copy of the 2007 edition, the news that there is now a second edition ("including corrections and emendations") need not drive us to complete despair as the online edition (free!) is the revised second edition.
Apart from NETS, you can pick up an English LXX in the form of the Orthodox Study Bible (with the unlikely publisher Thomas Nelson) as it still remains the official text of the Old Testament in the Eastern church. But if you really want a groundbreaking LXX, definitely consider Nicholas King's translation, which is being published in installments by Kevin Mayhew.