Uses tvrage.com's xml api to retrieve episode titles for a specific show and rename files accordingly.

ShowRename.py

import glob, os, urllib2, re
from xml.etree import ElementTree

# Input:	Takes in "S##E##.avi" or "S##E##.mkv"
# Output:	Renames to "S##E## - [Episode title].avi" (or mkv)

# Search: http://services.tvrage.com/feeds/search.php?show=Mythbusters for sid
show_id = 4605

# Get episode list from tvrage.com for the selected show
xml_data = urllib2.urlopen("http://services.tvrage.com/feeds/episode_list.php?sid=%d" % show_id).read()
xml_tree = ElementTree.fromstring(xml_data)

episodes = {}

# For each season in the xml tree
for season in xml_tree.findall("Episodelist/Season"):
    # Get the season number
    season_num = int(season.get("no"))
    # For each episode in the episode list of the current season
    for episode in season.findall("episode"):
        # Get the episode number and title
        episode_num = int(episode.find("seasonnum").text)
        episode_title = episode.find("title").text
        # Create the episode_code S##E##
        episode_code = "S%02dE%02d" % (season_num, episode_num)
        # Remove any illegal filename characters from the title
        episodes[episode_code] = re.sub("[\\/<>:|?*]", "", episode_title)

# Build a list of video files in the current directory
file_list = []
for extension in ["*.avi", "*.mkv"]: # Add whatever extensions you desire here
    file_list.extend(glob.glob(extension))

for file in file_list:
    # Get the filename and extension
    filename, extension = file.split(".")
    # Build new filename
    new_filename = filename + " - " + episodes.get(filename, "") + "." + extension
    # Display proposed rename
    print 'Renaming: "%s" -> "%s"' % (file, new_filename)
    
    # Comment this out for a dry run, then if the output
    # looks right uncomment and run to do actual rename
    # os.rename(file, new_filename)