Cemeteries in Buenos Aires are ultra-cool and interesting. Each tomb is a little building, or chapel, which makes the cemetery look like a miniature city with a little skyline. Of course you'll want to visit Recoleta cemetery, where Eva Peron is buried - her tomb is adorned with flowers from a constant barrage of well-wishers, along with plaques from various organizations. Though it's hard to find your way around the cemetery, follow groups of people and you're sure to find Evita's resting place.
The cemetery I found to be the most interesting was the larger Chacarita Cemetery. Famous people buried here include Carlos Gardel (the father of the Tango), and Juan Perón. Carlos Gardel's tomb is almost festive, and is adorned with a large statue of the musician. Be sure you ask someone to show you where it is, as this cemetery is much less touristy, so you can't find famous tombs by following crowds. A kind groundskeeper showed me the way to Gardel's tomb, then took me over to Juan Peron's, where, as luck would have it, there was a small group of people gathered around to celebrate his birthday (I had no idea it was his birthday when I went!) They sang songs, hugged and kissed each other, and didn't seem to mind that I was lurking about. What an experience! You have to take the subway to get to Chacarita Cemetery - ask at the tourist office.