Transportation

Metro line 4: reachable from 2 stations (Porte d'Orléans or Alésia, 5 min walk, pictured below). Gets you quickly to Montparnasse, Gare de l'Est, and other lines (10, 12, 3, 9, 5, 2), including the scenic line 6 to the Eiffel Tower.
* RER B train (fast subway line, above): cross the parc (diagonally, 5mn) to the Cité Universitaire station, or grab a bus to Denfert-Rochereau. This connects you directly to both Paris airports, train stations, and central places like Notre-Dame, Chatelet (10 min), Auber (Grands Magasins 'Galeries Lafayette' & Opera), Etoile (Champs Elysées & Arc de Triomphe) or Gare de Lyon.
* Tramway: the tramway 3(a) goes around Paris, connecting to metro lines 13, 7, 8 (using a same ticket).

BUS:  Direct Airport (Orly) bus at 100m, and Lines # 88 / 62 / 28 / 38 / 68.  http://www.ratp.fr/plan-interactif/cartebus.php
Nightime 'Noctiliens' at Porte d'Orléans (right)http://www.ratp.fr/plan-interactif/cartenoctilien.php 

TAXIS: are lined up at Porte d'Orléans, or can be called 5-10 min before your departure at +33-0-1.45.40.52.05 for pick up at the apartment. Count 1.5 euros/km, and supplements as of the 2nd suitcase or 4th person (1 euro/suitcase & 3 euros extra for a 4th person).  If you prefer to reserve a taxi we recommend the company G7 which, unlike Alha taxi, does not charge for reservations.  In addition to 01.47.39.47.39 they have an exclusively English line: 01.41.27.66.99

PARKING: Usually easy in front of the building, and free weekends or between 7pm-9am weekdays (and any time during August).  Nearby underground parking of Porte d'Orléans charges 26 euros/day otherwise, and permanently free spots can be found nearby on the 'Impasse David Weill'.

BIKE & CAR RENTALS: Autolib' (car city rental, pictured below: http://en.velib.paris.fr/) and Velib' (bike rental: http://www.autolib-paris.fr/) stations are meters away from the apartment.