If you're looking for a recent IPO that looks poised to break out, then take a look at Zipcar ( ZIP), which operates a car-sharing network. Zipcar provides over 400,000 members, also known as Zipsters, with self-service vehicles that are located in reserved parking spaces throughout the neighborhoods where they live and work. This stock is off to a weak start in 2011, with shares off by around 12%. If you take a look at the chart for Zipcar, you'll see that this IPO has just started to break out above a key descending trend line that had been acting as resistance on the stock for the past couple of months. In fact, anytime the stock traded near this descending trend line, it failed and immediately trended lower. Now the stock has started to trade above the trend line and it looks ready to make a big run higher. What trades should watch for now is for a big upside volume to start moving into this stock. I would suggest watching for upside volume that's well above its three-month average volume of 646,000 shares as ZIP starts to challenge some of its overhead resistance prices. Related: 5 Heavily Shorted Market Leaders Set to Soar One could simply be a buyer of this stock on any weakness as long as ZIP stays above the descending trend line. I would add to any long position once you see ZIP take out some near-term overhead resistance at $25 to $26.37 a share. A move above those levels could set the stock up for a run back toward its all-time highs of $30.80 a share. It's worth noting that this stock is heavily shorted by the bears. The current short interest as a percentage of the float for ZIP stands at 16.1%. The short-sellers have also been increasing their bets from the last reporting period by 19.7%, or by about 656,000 shares. This stock could easily be setting up to short squeeze big, so keep this name on your trading radar.