We saw R' Chaim Kanievsky at Mincha in the shul right by his house. If you know the right people you can get in for a private meeting/bracha, but this was enough for us. We also knocked on R' Shteiman's door, he has a gabbai who told us to wait a bit - eventually he let us in. R' Shteiman was farhering a class, which was interesting to watch, then he gave us each a quick bracha. R' Elyashiv gives a shiur somewhere in meah shearim, some of us went to the shiur which was very "lebedik". R' Wosner was in yerushalaim for a shabbos when we were there, i believe he gave a shiur in a shul called shevet levi near rechov shmuel hanavi. We saw the Belzer Rebbe in shul after kabbalos shabbos, everyone runs by, but i believe if you are a guest - you can stop and "say hello"! R' Yitzchok Soloveichik is almost always in his Yeshiva learning so if you want to talk in learning with a gadol that is the the place to go. You basically need to ask around - everyone has a friend of a friend who knows where and when to be etc....
one interesting place to see some rabbonim was motzai tisha b'av at the kosel. There are a number of Rebbe's that come to say kiddush levana and tons of bochurim following them around!
