If you plan to visit a number of museums and attractions, you should consider the Stockholm Card which includes access to many attractions plus transport around the city. Otherwise you should get a three day card with the local transport (SL) which is only 235 sek ($28).
When you travel to europe you really have to get these tourist cards. Sweden is probably the most expensive place in europe so getting this card will save you some money when trying to get around. Especially when a 2-mile cab ride is around $15. The stockholm card is definitely well worth it.
Places I suggest seeing in Stockholm The Stockholm Card is good but you really have to work hard to get value from it if you're only there a short period. Places I suggest seeing in Stockholm are Drottingholm Palace, Chinese Pavillion and Palace Theater, Skansen Park, Vasa Museum, City Hall Tour and Nobel Prize Museum. I would too recommend getting the SL Pass as it's worthwhile if you are going to use public transport more than a few times.