I travelled last year for a year with a backpack across asia, south and north america, and south africa.
here was my setup, made to be light and as unexpensive and helpful as it could be.
overall, you want stuff to supplement your trip, not replace it - your fear of missing your collection of MP3s on the go will soon vanish as you realize you don't need it as much after all - use the gear to enhance the experience by helping you discover the countries you visit and bringing back memories, and communicating with friends, instead of shielding you from the fear of boredom/cultural barriers/melancoly
the biggest thing is: bring things you can get parted from: it may be a little more difficult without them, but don't ruin your trip with security concerns.
everything expensive should be VERY light and small and you should keep it in your daypack all the time. max 1-2 kgs for everything. leave the laptop at home. you'll regret bringing it after 2 weeks of lugging around and fearing to get stolen.
I had: digital camera on AA batteries and plenty of sd card space
pocket pc with gps
ipod (for offloading pictures) but got stolen after 2 weeks in south america. at first I screamed but then I understood that I was actually better off without it as it was one less thing to constantly check and fear getting stolen...
the most important: usb key for cybercafes with proper setup
on the usb key: portable firefox and thunderbird with good confirguration and bookmarks, and accounts with passwords in keychain - no need to type them in cybercafes and have them sniffed!
portable filezilla - great for sending home on ftp server your most beloved pictures, and even more. in a typical 1-2h session in a cybercafe I could upload 50-100 pictures which made sure I wouldnt lose anything if somebody stole my camera. burning cds and sending home is feasable, but a hassle - you dont want to spend an afternoon every week doing that plus laundray, getting information, etc...
pstart - a practical self contained launcher for all of that
bookmarks with login info for my blog, etc... the different keyboard layouts can make typing passwords with **** a real hassle
if you have to type a password in a cybercafe, to avoid keylogger, type random keys in the adress bar then use copy paste to type in your password in the box
skype - can be launched without install
anti spyware and anti virus
PixaMSN or equivalent for chatting with friends
REST2514 - or similar software for recovering deleted files - you may want to have one handy
you want to have time to SEE and DO things - only spend the bare minimum in cybercafes and handling your tech gear, and enjoy the peoiple, the nature, the adventure
the gps is handy in a cab to check that you're taking a more or less straight route : i had my share of laughs indicating to a taximan I wouldnt pay because he made me run in circles, or better yet having coordinates of my destination and giving directions in a totally unfamiliar place to locals.
also the gps is of course extremely valuable in the wilderness
send copies of plane tickets, insurance forms, id card, passport to your email account - you'll be able to print them from anywhere needed
leave instructions for bankers-friends-family to handle your bank accounts and be able to make trasnfers to your visa cards, etc...
the most important asset will be your memories and your pictures: send them home through ftp, email, with web sites, or mail them. record sounds and conversations with the pda/ipod (you can install linux as dual boot on some models and get free mic with just the earphones) it's also very handy for recording messages while waiting for busses or around a campfire and sending them by email so you don't have to spend time writing lenghty descriptions - it also makes them vivid - with good compression you can send a 10 minute monologue for 2mb
also on the pda - extremely handy - various dictionaries: its much fastre to type in the first 3-4 letters than searching through the book - also bring things that will lighten your pack : travel guides (dump wiki travel on a 1gb sd card), dictionaries, comics and ebooks for the lonely night waiting for the bus or at the hostel when eveyrbody goes out and you want to be alone...
be fear free that somebody steals your gear - it may very well happento you, and you will survive, and if it does it should be a minor annoyance - if you dont own an ipod/camera/gps, buy a second hand one for cheap that makes just what you need, same for every investment you want to make - try to be detached from your stuff and you'll have such a better time
and dont risk your life for an mp3 player! if they want it, give it. In some countries they WILL stab you to get it easier.
But most of the time, the locals will be genuinely interested in the more interactive stuff, like showing them the pictures on the camera screen after taking them, or recording a local song they sing for you and playing it back.
also - dont forget to send your pictures to the people who asked for them! it's only a minor hassle for you, but such a pleasure for them - note the adresses carefully and send them to you by email once in a while