If you cant get into Lupa on a Saturday night...
If you aren't on a budget and want to have a great Northern Italian meal go to Da Umberto on 17th and 6th. They have been around for decades and are one of the most consistent (if not trendy) places I frequent.
Mauritzio on 13th between fifth and sixth is a local west villager that has very good food and is less pricey.
Also, there is a great little intimate spot called La Cantina on 8th and Jane.