Near Piazza Navonna, on the beautiful Piazza del Fico, you will find Bar Del Fico. Somewhat of an institution in Rome, this shabby-chic place is a hot spot to grab a drink and chill out. They have a great all you can eat aperitivo buffet, free with a 5 Euro glass of wine or 8 euro cocktail. Food is a bit hit and miss, so (apart form the aperitivo) I would just stick to a drink here. They might also have one of the most bizarre websites I have ever seen.
Piazza del Fico 26