I have put two examples of H.264 coded sequences on the downloads page. Both are short segments of the "Foreman" CIF video sequence, coded using the Baseline and Main profiles of H.264.

Use a viewer such as Elecard's Streameye to analyze the clips:

http://www.elecard.com/products/products-pc/professional/streameye/
(you can download a time-limited trial version).

Here's an screenshot of the Main Profile clip. You can see the P-slices (blue bars) and B-slices (green bars). Use the Streameye menus to examine frames, look at the distribution of macroblock types, motion vectors, etc.