iTunes doesn't charge a membership, they charge per download and the cost varies by product. A single song can be .99 or $1.49 or you can purchase the entire CD, the cost of which usually depends in it's age and how many songs are on it. Around $10 to $13 is average for mine. You can buy iMixes, which are compilations of songs with a theme such Love Songs of the 90s or Female Rapper #1 Hits. Some songs can be purchased and downloaded as ringtones for your phone.
If your iPod has video, you can buy movies and tv to watch on it. A single tv episode is usually $1.99 and the entire season for a hit show is usually $34.99. Other shows depend on how many episodes are available. Movies run about the same as buying the DVD would. Pirates of the Caribbean is $9.99. I don't have the video on my iPod and while occasionally it sounds like a fun thing to have I don't think I would use it enough to justify the cost.
I mainly use mine when I walk my dog or clean house. I keep relaxation music on it for when I'm having trouble sleeping or am feeling sick or getting yucky treatments at the hospital. Other than that, I'm just not one of those who goes around with her iPod stuck in her ears all the time. Flame away if you want but I'm apalled at how often and how many places I see people wearing them. Walking home from school is fine (although you should be able to hear traffic around you so either one ear should be uncovered or the volume low which you know isn't happening) but a 15 year old is quite capable of going to the grocery store with his/her mother to help with the shopping without having to be continuously entertained. And if she's in the mall trying to buy you clothes, you really might want to show a little respect and pay attention for just a couple hours
Couple more things, first thing you want to do when you get an iPod is probably throw away the earphones and get more comfortable ones. The ones they come with SUCK!!! For regular in ear headphones that are really comfortable try these
http://www.target.com/Skullcandy-Sm...e=1&index=tgt-mf-mv&rank=salesrank&rh=&page=1
For headphones that rest on the outside but don't enter the ear canal these are excellent
http://www.target.com/Sony-Silver-S...TF8&coliid=&frombrowse=1&alt_view=custReviews
And I highly recommend a cord spool, which keeps your headphone cords out of the way. Mine looks like a little rubber thread spool. LOVE IT! And yep, taking them to school is a BAD idea

But then, why would you want them to??