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I wanted to know which IP addresses are usually not assigned.
Here is a list of those I know are used for something.
[*]0.0.0.0 (are all other 0.x.x.x allowed?)
[*]127.x.x.x (all these are loopback aren;t they?)
[*]x.1.1.1 (multicast?)
[*]x.x.x.255 (broadcast)
[*]256.x.x.x (outbound addresses?)

Are these correct? and are there any others?

10.0.0.0 to 10.255.255.255, 172.16.0.0-172.31.255.255 and 192.168.0.0-192.168.0.255 are "IANA Reserved for private networks" [RFC1918]
192.0.2.0 to 192.0.2.255 are "IANA Test Net" [RFC3330]
And supposedly 224.0.0.0 to 255.255.255.255 are reserved for a combination of multicast and private network uses.

There are several reasonably long lists in the RFCs above of other addresses.

Neo wrote: I wanted to know which IP addresses are usually not assigned.
Here is a list of those I know are used for something.
[*]0.0.0.0 (are all other 0.x.x.x allowed?)
[*]127.x.x.x (all these are loopback aren;t they?)
[*]x.1.1.1 (multicast?)
[*]x.x.x.255 (broadcast)
[*]256.x.x.x (outbound addresses?)

Are these correct? and are there any others?

Nope, that's not correct.

0.0.0.0 is blank.
127.x.x.x is loopback, each of them (as denoted by 127.0.0.0/8)
224.x.x.x/4 is multicast (meaning the first 4 bits must be as given, or, 224.x.x.x - 239.x.x.x)
10.x.x.x/8 is local network, not to be routed.
192.168.x.x/16 is local network, not to be routed.

Broadcast is NOT always the .255 number. It depends on the subnet mask. If you have a /19, say for a reasonable company, such as:

19.159.160.x/19 -> 19.159.160.x - 19.159.191.x

with your IP being 19.159.171.42 your broadcast would still be 19.159.191.255, and not 19.159.171.255.

Your local broadcast is 127.255.255.255. (which broadcasts to you yourself, pretty much. It's pointless to know it but in a way it's true).

There is no 256.* since you can't squeeze the 9th bit of 256 (binary 100000000) in an 8-bit number (which is what IPv4 uses).

Candy forgot 172.16.0.0/12 (private, not to be routed), but otherwise, nice summary.

Edit: I found another one while googling. Mostly a retelling of the above...

Private IP's not to be routed:

10.0.0.0/8 (10.0.0.0-10.255.255.255)
172.16.0.0/12 (172.16.0.0-172.31.255.255)
192.168.0.0/16 (192.168.0.0-192.168.255.255)

Other reserved IP's never assigned to "public" networks include:

0.0.0.0/32 - Historical broadcast address
127.0.0.0/8 - Loopback
169.254.0.0/16 - Link-local Networks
192.0.2.0/24 - TEST-NET
224.0.0.0/4 - Class D Multicast address range
240.0.0.0/5 - Class E Experimental address range
248.0.0.0/5 - Unallocated
255.255.255.255/32 - Broadcast

Solar wrote: 0.0.0.0/32 - Historical broadcast address
127.0.0.0/8 - Loopback
169.254.0.0/16 - Link-local Networks
192.0.2.0/24 - TEST-NET
224.0.0.0/4 - Class D Multicast address range
240.0.0.0/5 - Class E Experimental address range
248.0.0.0/5 - Unallocated
255.255.255.255/32 - Broadcast

What is that Link-local networks

RFC 3330 says:

169.254.0.0/16 - This is the "link local" block. It is allocated for communication between hosts on a single link. Hosts obtain these addresses by auto-configuration, such as when a DHCP server may not be found.

That RFC mentions some other reserved areas, too.