Alex posted a link to a recent paper on the Malin/Edgett gullies:

Recent gullies on Mars and the source of liquid water
Michael T. Mellon and Roger J. Phillips
JGR Planets (2000JE001424)

HTML version
http://www.agu.org/journals/je/inpress/je001424_esrel/0.htm

PDF version
http://www.agu.org/journals/je/inpress/je001424_esrel/je001424.pdf

The authors also presented their results at the 32nd LPSC:

Title: Recent Gullies on Mars and the Source of Liquid Water
Authors: Mellon, M. T.; Phillips, R. J.
Journal: 32nd Annual Lunar and Planetary Science Conference, March 12-16, 2001, Houston, Texas, abstract no.1182
http://adsabs.harvard.edu/cgi-bin/bib_query?2001LPI....32.1182M [full text]

They present a model for how water could remain liquid in the subsurface at high latitudes. In this LPSC report they appear to be suggesting the gullies would have to be formed in periods of high angle of tilt in Mars obliquity cycle, because Mars would be too cold at the surface at those latitudes currently. However recent TES temperature measurements suggest the temperature on Mars can be above zero even at southern latitudes into the 60's:

http://wwwflag.wr.usgs.gov/USGSFlag/Space/MGS_TES/spole99.html

Then depending on the altitudes and pressures at these sites it is possible that liquid water could have flowed in current times at least for short times.

Bob Clark