I recently spent a month backpacking around western Europe. I didn't want to take my MacBook Pro with me (The kerfuffle with insurance if it was stolen outweighed my need for it), so my main source of information was my HTC Desire S. Here are a few notes on stuff I found was useful.
1. Improving battery life
One of the main let downs with Android is the crapware networks & manufactures put on the handset (in most cases you can't even uninstall it). So I rooted my phone & put CyanogenMod on it. Removing the unused apps gave me about 25% more battery per day.
I also put my phone in Airplane mode when I wasn't using it. I found having my phone in airplane mode used about 1/20 of the battery it would have if I didn't have airplane mode on.
2. Improve security
I was fairly paranoid about losing my phone, or my data while I was away. Here are a three apps & one technique I used to keep myself a little safer.
Prey lets you keep track of your stolen device via a web interface & in some cases you can take pictures of the people who have taken it. It's also free, so this seemed like a no brainer.
I didn't want to lose my photos, so I set up SugarSync to backup the photos I took while I was away, so if I did lose my phone, my photos will still be ok. It also meant that when I was home, my Mac had the photos I had taken already on it ready for me to sort through.
I used a a few shared wireless hotspots, quite a few of these offered some pretty interesting DNS servers. So I used Set DNS for rooted android phones to change the DNS servers to the one offered by Google (220.127.116.11, 18.104.22.168).
I also used a private VPN while I was traveling mostly because I wanted to keep my data secure from anyone listening over wifi or mobile network connections. If you have a VPS, you can install OpenVPN pretty easily (though make sure your VPS provider is ok about it).
3. Finding my way around
Before I went away, I was given a couple of books to help find my way about. However, carrying a big book around a city during the day seemed a little silly. Here are a few apps I used to help find my way around.
Google maps was pretty handy to find my way around town, I also found it was pretty handy to make "My Places" map in google maps to save a few useful locations (Like my hostel & cool things to do during the day). That said, google maps didn't cache the maps I made, so I had to keep downloading them every time I wanted to check it.
TripAdvisor & Lonely Planet
FourSquare was really handy for finding awesome places around the cities, though reading the reviews & checking in ate lots of data.
4. Dealing with data
Even with lower data roaming prices within Europe, the price of sending the odd tweet or checking google maps was silly. So I picked up a prepaid data sim (it's pretty easy to walk into a phone shop and ask for one, they should only cost a few euros for 1GB data) and used a Micro Sim Adaptor to make it work with my phone.
In most cities the signal was pretty awesome, I could download at about 100kb/s. That said, you may want to look into a picking up a unlocked MiFi to get more out of your SIM.
5. Making calls on the cheap
Calling & texting while traveling looked friggin expensive! However with the data sim I had & jumping onto free wifi, I used Viber (It's like Skype, but not a bloated OTT POS) to make calls & message people.