What's taking so much damn memory?

gistfile1.txt

top - 12:34:49 up 2 days,  8:53,  1 user,  load average: 0.00, 0.00, 0.00
Tasks:  24 total,   1 running,  23 sleeping,   0 stopped,   0 zombie
Cpu(s):  0.2%us,  0.0%sy,  0.0%ni, 99.7%id,  0.0%wa,  0.0%hi,  0.0%si,  0.0%st
Mem:    524288k total,   524288k used,        0k free,        0k buffers
Swap:   524288k total,   201484k used,   322804k free,        0k cached

  PID USER      PR  NI  VIRT  RES  SHR S %CPU %MEM    TIME+  COMMAND                                                     
 6118 lincomp   37   0  420m 322m 3164 S    0 62.9   0:51.90 ruby                                                        
 4597 root      34   0  314m 148m 4384 S    0 28.9   0:00.92 apache2                                                     
 4635 www-data  39   0  432m 147m 2272 S    0 28.8   0:05.38 apache2                                                     
12723 mysql     31   0  164m  40m 6264 S    0  8.0  39:30.44 mysqld                                                      
 4615 root      31   0 59648  15m 2140 S    0  3.0   0:00.48 ruby                                                        
 4618 nobody    31   0 72912 3788 3068 S    0  0.7   0:00.00 PassengerLoggin                                             
 4613 root      35   0 93116 3456 1940 S    0  0.7   1:03.55 PassengerHelper                                             
24106 root      31   0 66088 3180 2480 S    0  0.6   0:00.20 sshd                                                        
 5060 root      31   0 65940 3004 2388 S    0  0.6   0:00.00 sshd                                                        
14484 postfix   31   0 38940 2388 1880 S    0  0.5   0:00.01 qmgr                                                        
14468 root      31   0 36836 2276 1800 S    0  0.4   0:00.02 master                                                      
29949 postfix   31   0 38928 2204 1744 S    0  0.4   0:00.00 pickup                                                      
24108 root      31   0 20936 1936 1400 S    0  0.4   0:00.04 bash                                                        
 5063 files     31   0 42100 1848 1424 S    0  0.4   0:01.33 sftp-server                                                 
 4610 root      35   0 23184 1836 1580 S    0  0.4   0:00.01 PassengerWatchd                                             
 5062 files     31   0 65940 1636 1012 S    0  0.3   0:00.46 sshd                                                        
12686 root      21   0 17300 1428 1148 S    0  0.3   0:00.00 mysqld_safe                                                 
12643 root      34   0 99004 1416  980 S    0  0.3   0:00.86 rsyslogd                                                    
21089 lincomp   31   0 35372 1280  680 S    0  0.2   0:00.21 searchd                                                     
12651 root      31   0 48852 1192  704 S    0  0.2   0:00.67 sshd                                                        
15000 root      31   0 18812 1176  940 R    0  0.2   0:00.00 top                                                         
14486 root      31   0 18536  924  712 S    0  0.2   0:00.01 cron                                                        
    1 root      15   0 10304  752  628 S    0  0.1   0:03.87 init                                                        
12724 root      34   0  3772  588  504 S    0  0.1   0:00.00 logger