Pretty much all of Westchecter comes to mind if you don't mind living a little further south (but as close to or closer to the beach.) Ladera Heights and parts of the Baldwin Hills and North Inglewood all fall loosely into this category as well. I expect major appreciation in all of these overlooked areas that are actually quite close to the beach.
As far as the Westside proper is concerned, I think that the best undervalued area to buy in now is just east of the Marina to Centinela ,between Washington and Culver. This area can also be expanded to include much of Mar Vista and Palms and the western portions of Culver City. I would also take a look at the small group of 1950's tract homes just north of Jefferson and around Balona Creek.
That being said, I'd personally be looking at fixers in Venice and Marina del Rey. Beach premiums have been slipping lately and I've see some really good properties here for under $700k for homes on full lots.
Below is a link to my website where you'll find all the properties listed for sale on the Westside and Beach Cities. Please feel free to contact me if you have more questions about these areas or need any special property searches run for you. Best of Luck.