Amazon is sunsetting SSLv3 support soon, and I am trying to verify that boto is utilizing TLS. Is there a good way to verify this? Or is there a good test to show TLS utilization?
As stated above, you can use a packet sniffer to determine if SSLv3 connections are being made:
# sudo tcpdump -i eth0 'tcp[((tcp[12]>>4)*4)+9:2]=0x0300'
Replace 'eth0' with the correct interface. Then test if it's working, by performing a SSLv3 connection with openssl:
# openssl s_client -connect s3.amazonaws.com:443 -ssl3
That activity should be captured by tcpdump, if network interface is correct. Finally, test your app. If it's using SSLv3 it should be visible as well. You can also change the capture filter to see what protocol is being used:

TLSv1 - 0x0301 
TLSv1.1 - 0x0302 
TLSv1.2 - 0x0303
How to tell if boto is using SSLv3 or TLS?