How can I see my IPv6 neighbors? On a Linux machine, I can see my IPv6 neighbors using the following command (Also see the Linux IPv6 HOWTO:

    # ip -6 neighbor show
    2002:333:333::1 dev eth1 lladdr 00:12:1e:33:AA:BB router REACHABLE


What is the equivalent command on a Mac (currently running Snow Leopard)?
Short answer:

mir:~ itorres$ ndp -an
Neighbor                        Linklayer Address  Netif Expire    St Flgs Prbs
::1                             (incomplete)         lo0 permanent R      
2001:470:95e5:1:3583:ead0:514d:d459 e8:6:88:ca:fd:7c en0 permanent R      
2001:470:95e5:1:ea06:88ff:feca:fd7c e8:6:88:ca:fd:7c en0 permanent R      
...


Longer answer:

You're in UNIX and you have two great commands: man (system manual) and apropos (lookup concepts on manual)

Hence:

mir:~ itorres$ apropos ipv6
Net::CIDR::Lite(3pm)     - Perl extension for merging IPv4 or IPv6 CIDR addresses
Net::IP(3pm)             - Perl extension for manipulating IPv4/IPv6 addresses
NetAddr::IP(3pm)         - Manages IPv4 and IPv6 addresses and subnets
NetAddr::IP::Lite(3pm)   - Manages IPv4 and IPv6 addresses and subnets
faith(4)                 - IPv6-to-IPv4 TCP relay capturing interface
icmp6(4)                 - Internet Control Message Protocol for IPv6
inet6_opt_init(3), inet6_opt_append(3), inet6_opt_finish(3), inet6_opt_set_val(3),     inet6_opt_next(3), inet6_opt_find(3), inet6_opt_get_val(3) - IPv6 Hop-by-Hop and     Destination Options manipulation
inet6_option_space(3), inet6_option_init(3), inet6_option_append(3), inet6_option_alloc(3    ), inet6_option_next(3), inet6_option_find(3) - IPv6 Hop-by-Hop and Destination Options     manipulation
inet6_rth_space(3), inet6_rth_init(3), inet6_rth_add(3), inet6_rth_reverse(3),     inet6_rth_segments(3), inet6_rth_getaddr(3) - IPv6 Routing Header Options manipulation
inet6_rthdr_space(3), inet6_rthdr_init(3), inet6_rthdr_add(3), inet6_rthdr_lasthop(3),     inet6_rthdr_reverse(3), inet6_rthdr_segments(3), inet6_rthdr_getaddr(3),     inet6_rthdr_getflags(3) - IPv6 Routing Header Options manipulation
ip6(4)                   - Internet Protocol version 6 (IPv6) network layer
ip6(8)                   - Enable or disable IPv6 on active interfaces
ip6config(8)             - Configure IPv6 and 6to4 IPv6 tunnelling
ip6fw(8)                 - controlling utility for IPv6 firewall (DEPRECATED)
ndp(8)                   - control/diagnose IPv6 neighbor discovery protocol
tcllib_ip(n)             - IPv4 and IPv6 address manipulation
traceroute6(8)           - print the route IPv6 packets will take to a network node


To get more detail about ndp:

mir:~ itorres$ man ndp