I spent one day in Lima, so here are my highlights:

- I thought the 'changing of the guards' ceremony at the Presidential Palace was really neat. It's not given much mention in the tourbooks. Think Buckingham Palace but with lots of gun tossing and an elaborate South American band. I believe that it's at noon every day.

- I'll second the prior rec for the Larco museum. The erotic art gallery is unlike anything I've never seen before.

- The catacombs were awesome to see (if you're not the type who would be grossed out by that). They're at the church near the Plaza de Armas.

- Eat as much ceviche as you can. It wasn't nearly as good in other parts Peruvian cities, and what is called "ceviche" in the US isn't anything close.

I hit all the major things (Plaza del Armas, the main cathedrals, Park Kennedy, etc.), but the above is what stands out and what I remember most.