According to the search results, the following maps were available in the Modern Warfare 3 beta:

• Favela
• Skidrow
• Estate
• Rust (only during the open beta period)
• Highrise (only available during the second weekend of the beta)

Its worth noting that all 16 classic Modern Warfare 2 maps were playable in Modern Warfare 3 at launch, but players could only revisit a few iconic locations in the beta.