The translations from The Mahabharata by W.J.Johnson and published in Oxford World's Classics series are highly recommended. There are two;
1) The Bhagavad Gita - A very nice and succinct translation that you can read and re-read many times. Pair it with the more detailed 2-vol translation by Franklin Edgerton and you can understand the text better.
2) The Sauptikaparvan of the Mahabharata: The Massacre at Night - This is an excellent and rare translation (pdfs available online) of a section from the end of the Mahabharata where after the defeat of the Kauravas in War, Ashwatthama with his two other colleagues sets out to eradicate the entire progeny of the Pandavas in revenge. With colourful and evocative language it paints a good picture of all the doom and gloom at the end of the epic.