Smashing Magazine conducted a small study on the designs of big blogs. This study contains

1. Columns

2. Alignment

3. Fixed or elastic

4. Width of fixed

5. Proportion between the content area and layout

6. CSS-layout or table-based layout

7. Dark on light or light on dark

8. characters per line

9. Primary typeface for body text

10. font size of headlines

And few more details, the conclusion was

• large blogs require a multi-column layout solution (usually 3 columns suffice) (58%);
• layouts are usually centered (94%),
• layouts usually have a fixed width (px-based) (92%),
• the width of the fixed layout varies between 951 and 1000px (56%),
• 58% of the overall site layout is used to display the main content,
• CSS-layouts are used (90%),
• the background is light, the body text is dark (98%),
• the most usual (not necessarily most user-friendly) line length lies between 80 and 100 characters,
• Verdana, Lucida Grande, Arial and Georgia are used for body text (90%),
• the font size of body text varies between 12 and 14px (78%),
• Arial and Georgia are used for headlines (52%),
• headlines have the font size between 17 and 25px.

Don’t forget to check the actual post it contain few more details and some more studies also.