A company called Slate Computing (said to be a front company for Apple) registered for the iPad trademark in Canada in July. Similar trademark filings were made in Europe and Hong Kong in the same month.
In the US Fujitsu owns the iPad trademark for handheld computing. Macrumors suggests that this won't stop Apple getting the trademark - as was the case when Apple won the iPhone trademark that was owned by Cisco.
According to Macrumors, in the past week there have been new iPad trademark applications in New Zealand and Australia, made by a company registered as IP Application Development.
The iSlate trademark was registered back in 2006.