Nginx sslv3 poodle disable

You could have multiple server blocks. So just add new server block for domains that need HSTS.

server {
    listen xx.xx.xxx.xxx:443 ssl default_server;

    # all ssl stuff
    # and other directives
}

server {
    listen xx.xx.xxx.xxx:443 ssl;
    server_name example.com other.example.com;

    # all ssl stuff
    # and other directives with HSTS enabled
}

Here first block will handle all https connections except example.com and other.example.com.

And you don't need ssl on directive if you have ssl flag in listen.

EDIT

There is another solution with only one server block:

map $scheme:$host $hsts_header {
    default "";
    https:example.com "max-age=31536000";
    https:other.example.com "max-age=31536000";
}

server {
    server_tokens off;

    listen xx.xx.xxx.xxx:80;
    listen xx.xx.xxx.xxx:443 ssl;

    ssl_certificate /etc/ssl/foo.crt;
    ssl_certificate_key /etc/ssl/private/foo.key;

    ssl_session_timeout 10m;

    # ... other ssl stuff

    location / {
        proxy_pass http://127.0.0.1:81;
        proxy_set_header X-Real-IP $remote_addr;
        proxy_set_header X-Forwarded-For $proxy_add_x_forwarded_for;
        proxy_set_header X-Forwarded-Proto $scheme;
        proxy_set_header X-Forwarded-Port $server_port;
        proxy_set_header Host $host;
        add_header X-XSS-Protection "1; mode=block";
        add_header Strict-Transport-Security $hsts_header;
    }
}

We use map to define HSTS header value and use the fact, than nginx will not add header with empty value.

No, it will not break HTTPS connectivity to your website; TLSv1 (and newer versions, if your software is recent enough) is already being used instead by almost all browsers (with the notable exception of IE6 on Windows XP).

Verify in your configuration that TLSv1 is enabled, but it is by default in almost every server-side SSL configuration.