It seems that Mars Global Surveyor has been out of communication for a week (also see here). MGS has been sending back bountiful information from its orbit around Mars for almost 10 years, so has had a very good run. Hopefully contact can be regained and it'll have another few years of dutiful service sending us piccies of Mars' surface. If not then I'll raise a glass to all it's achievements and say a fond farewell to a great spacefarer.
[Update - NASA have conceded that they are very unlikely to regain communication with MGS - I'll raise that glass when I next have a drink to hand.]