[buwaya]

My theory is that they were like Basques (also an isolate).

They were much more interesting than Basques though.

[Cronos]

like the BAsques

An interesting bit of research found that the Basques are not genetically different from their neighbours, only linguistically. Of course, being a small population they must have intermingled with the communities around them. The basque language is also supposed to be related to the Chechen. The other non-IndoEuropean linguistic group in Europe is the Finnish-Ugaritic group to which Finnish and some Baltic languages belong.

Weren't the Celts also Indo-European? Not Aryan though.

[Cronos]

Found this list of Indo-European language groups:

Subfamily	Group	Subgroup	Languages and Principal Dialects
Anatolian			Hieroglypic Hittite*, Hittite (Kanesian)*, Luwian*, Lycian*, Lydian*, Palaic*
Baltic			Latvian (Lettish), Lithuanian, Old Prussian*
Celtic	Brythonic		Breton, Cornish*, Welsh
Celtic	Continental		Gaulish*
Celtic	Goidelic or Gaelic		Irish (Irish Gaelic), Manx*, Scottish Gaelic
Germanic	East Germanic		Burgundian*, Gothic*, Vandalic*
Germanic	North Germanic		Old Norse* (see Norse): Danish, Faeroese, Icelandic, Norwegian, Swedish
Germanic	West Germanic (see Grimm's law)	High German	German, Yiddish
Germanic	West Germanic (see Grimm's law)	Low German	Afrikaans, Dutch, English, Flemish, Frisian, Plattdeutsch (see German language)
Greek			Aeolic*, Arcadian*, Attic*, Byzantine Greek*, Cyprian*, Doric*, Ionic*, KoinE*, Modern Greek
Indo-Iranian	Dardic or Pisacha		Kafiri, Kashmiri, Khowar, Kohistani, Romany (Gypsy), Shina
Indo-Iranian	Indic or Indo-Aryan		Pali*, Prakrit*, Sanskrit*, Vedic*
Indo-Iranian	Indic or Indo-Aryan	Central Indic	Hindi, Hindustani, Urdu
Indo-Iranian	Indic or Indo-Aryan	East Indic	Assamese, Bengali, Bihari, Oriya
Indo-Iranian	Indic or Indo-Aryan	Northwest Indic	Punjabi, Sindhi
Indo-Iranian	Indic or Indo-Aryan	Pahari	Central Pahari, Eastern Pahari (Nepali), Western Pahari
Indo-Iranian	Indic or Indo-Aryan	South Indic	Marathi (including major dialect Konkani), Singhalese (Sinhalese)
Indo-Iranian	Indic or Indo-Aryan	West Indic	Bhili, Gujarati, Rajasthani (many dialects)
Indo-Iranian	Iranian		Avestan*, Old Persian*
Indo-Iranian	Iranian	East Iranian	Baluchi, Khwarazmian*, Ossetic, Pamir dialects, Pushtu (Afghan), Saka (Khotanese)*, Sogdian*, Yaghnobi
Indo-Iranian	Iranian	West Iranian	Kurdish, Pahlavi (Middle Persian)*, Parthian*, Persian (Farsi), Tajiki
Italic	(Non-Romance)		Faliscan*, Latin, Oscan*, Umbrian*
Italic	Romance or Romanic	Eastern Romance	Italian, Rhaeto-Romanic, Romanian, Sardinian
Italic	Romance or Romanic	Western Romance	Catalan, French, Ladino, Portuguese, Provençal, Spanish
Slavic or Slavonic	East Slavic		Belorussian (White Russian), Russian, Ukrainian
Slavic or Slavonic	South Slavic		Bulgarian, Church Slavonic*, Macedonian, Serbo-Croatian, Slovenian
Slavic or Slavonic	West Slavic		Czech, Kashubian, Lusatian (Sorbian or Wendish), Polabian*, Polish, Slovak
Thraco-Illyrian			Albanian, Illyrian*, Thracian*
Thraco-Phrygian			Armenian, Grabar (Classical Armenian)*, Phrygian*
Tokharian (W China)			Tokharian A (Agnean)*, Tokharian B (Kuchean)*

[monkeyman81]

My theory is that there is a connection between Etruscan and Pelasgian(the pre-Indo-European -inthos or -ossos/-assos substratum of Greek, which may be related to Minoan.) I have little evidence for this, but it makes a lot of sense.
Pelasgian may be related to the Hurro-Urartian languages (the ancient languages of NE Anatolia, where M172 and related Y chromosome markers are found) which are thought to be NE Caucasian.
Genetic data shows that for Greece there is an association between the M172 Y chromosome marker that is associated with expansion from Anatolia to SE Europe and regions of intensive Neolithic settlement.
Here's the link:
http://www.santafe.edu/files/gems/ehlchronology/king.pdf
I wonder what genetic studies (esp. Y chromosome) of the Etruscan remains (or modern rural people from Tuscany and Umbria) would show.