Rabbi Hershel Schachter is among the most masterful teachers of Torah I have had the privilege to see and hear in action. Below, I have assembled links to various recordings of his shiurim available online. These links are to web pages which themselves contain one or more links to recordings of Rabbi Schachter.
This list is undoubtedly incomplete. If you know of any shiurim available online in audio or video format that are not already linked to here, please let me know in a comment, and I will add the link.
If you possess a recording of a shiur (or many shiurim) by Rabbi Schachter or other YU-associated rabbis which you think is not currently available online, please inform me of that as well, and I will try to arrange to have it made available online.
Links to sites that link to shiurim:
Adath Israel Poale Zedek Anshei Ozeroff: http://www.adathcongregation.org/audio_classes.html
Kehillas Bais Yehudah Tzvi of Cedarhurst: http://kbyt.libsyn.com/?search_string=schachter&Submit=Search&search=1
Kerem B'Yavneh: http://www.kby.org/torah/filterpage.cfm?type=all&ram=other&language=both&medium=both&date=all&topic=all&sort=TopicRam
OU: http://www.ou.org/ and search for "Schachter".
Torahspace (several pages of links): http://www.torahspace.com/c/All/
YU Torah: http://www.yutorah.org/searchResults.cfm?types=ALL&length=ALL&publication=ALL&categories=ALL&teacher=80153&masechta=ALL&fromDaf=&toDaf=&series=ALL&dates=ALL&language=ALL&keywords=&submitType=advanced