Here in San Diego we have a few breweries that are doing "session" or low ABV IPAs... these are lower alcohol IPAs with strong hop notes that emphasize the flavor of the selected hops. They tend to be lower in malts, thus being less "balanced" than a pale ale. These IPAs might be pale ales, except for the focus on the strong hops flavor and aroma.

Stone has one called "Stone to go IPA" ABV of 4.5
Rough Draft has a very nice IPA called "Weekday IPA" with ABV of 4.8 featuring Simco and Citra hops... for an IBU of 43 (low for an IPA). It is quite refreshing, easy on the tongue, with a nice hint of citrus.

Coronado Brewing Company and Green Flash have also had session IPAs.

On a similar note, albeit not as low in alcohol are the "Bachelor" series of IPAs from Societe Brewing... with ABVs of about 6.5, this series is unique in that it focuses on a single hop... which allows one to really taste the notes of that particular hop flavor. I am quite partial to "Citra" myself.