rotating xticks causes the ticks partially hidden in matplotlib
One good option is to rotate the tick labels.
In your specific case, you might find it convenient to use figure.autofmt_xdate() (Which will rotate the x-axis labels among other things).
Alternatively, you could do plt.setp(plt.xticks()[1], rotation=30) (or various other ways of doing the same thing).
Also, as a several year later edit, with recent versions of matplotlib, you can call fig.tight_layout() to resize things to fit the labels inside the figure, as @elgehelge notes below.
plt.tight_layout()But be sure to add this command after plt.plot() or plt.bar()
Setting the bounding box when saving will also show the labels:
figure.savefig('myplot.png', bbox_inches='tight')