The Soviet Union/Unified Team would have won 171 medals

If the Soviet Union would not have broken up, they would have won the most medals in the Beijing Olympics. (H/T to reader Sera Jones and wisegeek)

There would have been some reduction or shifts in the medal total
Because a unified team would not have been able to send multiple teams to rhythmic gymnastics to win gold and bronze and would only have won gold A combined team would probably had stronger relay teams in track and field and in swimming. However, this could have been made up by having stronger teams in gymnastics for the men and women team results.

Reuters has an article which talks about China breaking up the old duopoly in Olympic medals. China would have had more gold medals than even a unified Soviet team. China will need to wait until 2012 to exceed the USA and a hypothetical unified team in total olympic medals.

Country Golds Silvers Bronzes Total Medals
Russia 23 21 28 72
Ukraine 7 5 15 27
Belarus 4 5 10 19
Kazakhstan 2 4 7 13
Azerbaijan 1 2 4 7
Georgia 3 0 3 6
Uzbekistan 1 2 3 6
Armenia 0 0 6 6
Lithuania 0 2 3 5
Latvia 1 1 1 3
Estonia 1 1 0 2
Kyrgyzstan 0 1 1 2
Tajikistan 0 1 1 2
Moldova 0 0 1 1
Totals 43 45 83 171

FURTHER READING
China appears headed towards Olympic medal dominance

The GDP and population if the Soviet Union still existed.

The Soviet Union/Unified Team would have won 171 medals

If the Soviet Union would not have broken up, they would have won the most medals in the Beijing Olympics. (H/T to reader Sera Jones and wisegeek)

There would have been some reduction or shifts in the medal total
Because a unified team would not have been able to send multiple teams to rhythmic gymnastics to win gold and bronze and would only have won gold A combined team would probably had stronger relay teams in track and field and in swimming. However, this could have been made up by having stronger teams in gymnastics for the men and women team results.

Reuters has an article which talks about China breaking up the old duopoly in Olympic medals. China would have had more gold medals than even a unified Soviet team. China will need to wait until 2012 to exceed the USA and a hypothetical unified team in total olympic medals.

Country Golds Silvers Bronzes Total Medals
Russia 23 21 28 72
Ukraine 7 5 15 27
Belarus 4 5 10 19
Kazakhstan 2 4 7 13
Azerbaijan 1 2 4 7
Georgia 3 0 3 6
Uzbekistan 1 2 3 6
Armenia 0 0 6 6
Lithuania 0 2 3 5
Latvia 1 1 1 3
Estonia 1 1 0 2
Kyrgyzstan 0 1 1 2
Tajikistan 0 1 1 2
Moldova 0 0 1 1
Totals 43 45 83 171

FURTHER READING
China appears headed towards Olympic medal dominance

The GDP and population if the Soviet Union still existed.