I have a 2010 Prius II that I purchased used from a dealer with 19,100 miles on it last year. It now has about 34,700 miles on it. I haven't done anything to it except to get 2 oil changes and put in a new K&N air filter. Is there any service I can get done at the dealership for free before the car goes out of warranty at 36,000 miles?
no. you need a "service" agreement for that. now, on a used car, most dont have a "new car" warranty unless it is specifically added as part of the sale. did you get one? if its a CPO from a Toyota dealer, you probably did. but alas, if it aint broke, they wont fix it
If you did not get a copy of the Maintenance and Warranty Manual with the car you need to go to the Toyota Owner's website and download a copy. This lists the recommended maintenance for each 5k interval and also gives a detailed list of what is covered under the different warranty periods. You need to understand what is covered and what is not, especially the high cost hybrid components as stated above. But as stated above there are no free services available before the 36k miles.
Check to see if you need any of the work covered by TSBs which are FREE during the 36K warranty, but will cost you after 36K, i.e. engine undercover replacement. There is a list of the applicable TSBs on this site.