To make it I have implemented a script scrapping all the web pages of the site (the urls of the pages have a simple format) to extract the url of the flv file from the HTML, download those files and convert them to a typical avi format.
This is the python script, feel free to adapt it to your needs:
import urllib2
import os
import re
base = "http://www.marielilasagabaster.net"
for id in range(1, 422):
page = urllib2.urlopen(base + "/melodias.php?id=" + str(id))
html = page.read()
m = re.search("so.addVariable\(\"file\",\"(.*)&autostart=true\"\);", html)
print "Downloaded HTML Page " + str(id)
if m:
print "Found flv reference " + m.group(1)
url = base + m.group(1)
output = "video_" + str(id) + ".avi"
os.system("wget \"" + url + "\" -O - | ffmpeg -i pipe: " + output)