Microsoft has more than $50 billion in cash and liquid investments, but more than 80% of it is parked overseas -- mostly in Ireland -- for tax reasons.

If Microsoft brought some of that cash home -- say, to pay a bigger dividend -- it would face a big tax bill.

But if Microsoft uses that cash to buy non-U.S. companies, it never has to be repatriated.

In fact, Steve Ballmer specifically mentioned that Skype is based in Luxembourg in the press conference announcing the takeover, and said that it was an appropriate use of the company's cash.

Add to that Microsoft's recent multibillion dollar deal with Nokia and its 2008 acquisition of Norway's FAST for $1.2 billion -- its last big buy before Skype -- and it's clear that Europe is on Microsoft's radar.

So which other European companies might be a good use of the company's overseas assets?