They've started filming it already: http://www.imdb.com/title/tt0970416/
"Say 'Gort...Keanu...whoa...'"
Blade Runner was an adaptation of Dick's Androids novel, any remake would be VERY different.
As for Rama: http://www.imdb.com/title/tt0134933/
That won't be till next year though, apparently. Not sure how the strike might have affected either of these, though.
I think Clarke's "Childhood's End" would have been a great film, but "V" and "Independence Day" have kind of ruined that.
I love Asimov's Foundation series, but I can't see it made into a film easily. The Robot novels, however, hold some promise. "Caves of Steel" would be a great film, and then there are 3 sequel books to follow.