I am one of the stricter parents in our kids' circle and a lot of what you're asking depends on the child and how you parent them with everything. I hated having "arbitrary" ages for things when I was a kid and so I try to base my "when you're x age, you can..." on some reasonable decisions AND conversations with my kids. Also, my kids are both great at self monitoring. My son will play Wii for awhile and then turn it off and go open a book - that's without me saying a thing to him about it. My daughter has a limited text message package for her cell and never goes over her limit.
We have made decisions that are quite a bit earlier than the ages you've listed but mostly for some specific reasons or based on the conversations/decisions for each thing. My daughter will be 14 and my son 11 next month.
IPod - daughter received one (a shuffle) as a gift around 10 years; 11 year old son still doesn't have one but maybe for Christmas this year; they both would love iphones but neither will get them for several years (mostly due to cost)
Cell Phone - 10 when daughter began walking 1 block from school to choir rehearsal and then 1 block from choir to my office; son at 10 for similar reasons
Handheld game device (ie Nintendo DS, PSP) - around 7 or 8; at 14 and 11, they rarely use them except for in the car on long trips; my 11 year old son ALWAYS brings a book with him in the car, rarelly his PSP or DS
Full Gaming system (Wii, PS3, Xbox 360) - we still don't have one but mostly because they haven't expressed interest; we love our Wii
Thier own computer/laptop - daughter bought one with her own money when she was 11 and it is used by the rest of the family regularly; she will get a smaller one for 8th grade graduation this summer (to have for HS); will likely buy a laptop for son this year or next at age 11 or 12
Unmonitored but Restricted Interet - our rules are that they can use the computer when we are not in the room but we have to have access to everything they do (passwords, history of what they visited, etc.); so it's sort of unmonitored, sort of monitored; and I do check things regularly including my 14 year old's email account (11 year old has one but doesn't use it)
Unrestricted Internet Acess - totally agree on this one - at age 18 (will be at college where I won't have access anyway)
Email - 14 year old started at 10-11 years old but I have access, passwords, etc.; 11 year old has one but doesn't use it at all
Facebook/MySpace/Twitter - my kids never got into MySpace; daughter got Facebook at 13 (which is Facebook's rule); no Twitter because she isn't interested (doesn't want to use her precious text limits); 11 year old son not on at all (no interest) and for both I will have all acccess until age 18
A friend at work and I were just talking about how parenting younger children is more difficult in some ways (definitely more physically demanding) but parenting children as they get older is infinitely more complicated and nuanced. Your question (and the variety of responses) illustrates one of the many tricky areas of parenting tweens and teens.
Good luck. Talk with your kids, explain your reasons, listen to what they have to say and you'll make the right decisions about what ages for what things. Also, have consequences for if they don't follow the rules and follow through.