There have been several papers and many abstracts. The reason results seen slow coming in is that it takes a lot of work to process radar data.

So far both radars have elucidated the subsurface structure of the northern plains, the polar caps, the Medusa Fossa formation. Marsis has also looked at Phobos and done a lot of surveys of the ionospheric structure of Mars. They have not succeeded in finding liquid water, at least at a scale and depth resolveable by the radars.

Some abstracts:

http://www.cosis.net/abstracts/EGU20...pdf?PHPSESSID=

http://www.agu.org/cgi-bin/wais?dd=P13C-02

http://www.agu.org/cgi-bin/wais?jj=P14B-04

http://www.cosis.net/abstracts/EGU20...07-J-04682.pdf

http://www.agu.org/cgi-bin/wais?jj=P14B-02

http://www.agu.org/cgi-bin/wais?jj=P11B-0544

http://www.agu.org/cgi-bin/wais?jj=P14B-03

http://www.agu.org/cgi-bin/wais?jj=P11B-0545

Using Google scholar you can find many more.

Jon