A couple of other possible solutions are:
ls = {{1, {2, 3}}, {4, {5, 6}}, {7, {8, 9}}};
TableForm[Flatten /@ ls, TableDirections -> Row]
Or maybe:
ls = {{1, {2, 3}}, {4, {5, 6}}, {7, {8, 9}}};
TableForm[# /. {a_, b__} -> {a, Column[b]} & /@ ls,
TableDirections -> Row]
Hope this helps,
Ian