The wp_list_bookmarks() function is rather expensive. It provides the Blogroll sidebar block.
If we don't care about that and remove the call from wp-content/themes/default/sidebar.php we are now at:
~> siege -b -t30s -c5 http://wp1.localhost
** SIEGE 2.68
** Preparing 5 concurrent users for battle.
The server is now under siege...
Lifting the server siege... done.
Transactions: 1000 hits
Availability: 100.00 %
Elapsed time: 29.76 secs
Data transferred: 1.97 MB
Response time: 0.15 secs
Transaction rate: 33.60 trans/sec
Throughput: 0.07 MB/sec
Successful transactions: 1000
Failed transactions: 0
Longest transaction: 0.58
Shortest transaction: 0.07