Illyria was in Classical antiquity a region in the western part of today's Balkan Peninsula, inhabited by tribes of Illyrians, an ancient people who spoke the Illyrian Language. The delineation of ancient Illyria can pose a problem to historians, since before the Roman conquest the Illyrians were not unified into an Illyrian kingdom, and Illyria's borders before Rome are not always clear. For example, the
Dalmatae, though classed as an Illyrian tribe by language, were only subject to the kingdom of Illyria for a short time and soon defected during the reign of
King Gentius.
Illyrians. The Illyrians formed several kingdoms in the central Balkans, and the first known Illyrian king was Bardyllis. Illyrian kingdoms were often at war with ancient Macedonia, and the Illyrian pirates were also a significant danger to neighbouring peoples. At the delta of Neretva, there was a strong Hellenistic influence on the Illyrian tribe of Daors. Their capital was Daorson located in
Ošanići near Stolac in Herzegovina, which became the main center of classical Illyrian culture. The Illyrians even conquered Greek colonies on the Dalmatian islands. Queen Teuta of
Issa was famous for having waged wars against the Romans. Ultimately, the Romans subdued the Illyrians during the 1st century BC.
Illyrian Kingdom. After Alexander's death in 323 BC, independent Illyrian kingdoms again arose. In 312 BC,
King Glaukias seized Epidamnus. By the end of the 3rd century BC, an Illyrian kingdom based in Scodra (now a city in Albania) controlled parts of northern Albania, Montenegro, Herzegovina under
Queen Teuta, Illyrians attacked Roman merchant vessels plying the Adriatic Sea and gave Rome an excuse to invade the Balkans. In the
Illyrian Wars of 229 BC and 219 BC, Rome overran the Illyrian settlements in the Neretva river valley and suppressed the piracy that had made the Adriatic unsafe. In 180 BC, the Dalmatians declared themselves independent of the Illyrian
king Gentius, who kept his capital at Scodra. The Romans defeated Gentius, the last king of Illyria, at Scodra in 168 BC and captured him, bringing him to Rome in 165 BC. Four client-republics were set up, which were in fact ruled by Rome. Later, the region was directly governed by Rome and organized as a province, with Scodra as its capital.
Religion. The Illyrian town of Rhizon (Risan, Montenegro) had its own protector called Medauras, depicted as carrying a lance and riding on horseback. Human sacrifice also played a role in the lives of the Illyrians. The most common type of burial among the Iron age Illyrians was tumulus or mound burial. The kin of the first tumuli was buried around that, and the higher the status of those in these burials the higher the mound. (so, guys were barbarians, after all

)
Other interesting links:
http://en.wikipedia.org/wiki/Illyrian_warfare
http://en.wikipedia.org/wiki/Agron_(king)
http://en.wikipedia.org/wiki/Liburni
First two maps refer to language groups, but are indicative in terms of influence on Illyrian tribes. The last two maps are self-explanatory.