You can read Danny Outlaw's extensive blog entry here, but, in a nutshell, here's his list with my comments:
Picture storage: Flickr
You can't go wrong with Flickr, but photo sharing isn't really a "work" activity for most people.
Online data storage: Media Max
The big advantage of Media Max is that it's free, and offers a lot of storage -- 25 GB. However, backup is too important for some of us to trust a small company that's not charging anything. I use Jungle Disk, which isn't free but is very, very cheap, and that serves as a front end to Amazon.com's S3 service, which is super reliable and secure. Here's more about Jungle Disk.
I used Skype on my previous trip, but I'm currently looking for an alternative. Their service is OK, but customer service and billing headaches have ruined the experience for me. Any advice?
Snail Mail: Earth Class Mail
I've just recently signed up for Earth Class Mail. They give you a new address, and all your mail goes to them. They scan both sides of the envelope and put all scans in an online list. You can look at the envelope and, click to tell them to trash it (recycle it, actually), open and scan the insides, archive it and other options. It's a way to make paper mail electronic, and a Godsend for people who travel constantly. Here's more about Earth Class Mail.
Office Software: Zoho
I haven't tried Zoho, have you? I've been using Google Docs and I'm very happy with it. I especially like Google Doc's versions feature, where you can go back in time and access any previous saved version of your documents very easily. Here's more on Google Docs. However, my cursive glance at ZoHo was intriguing. In addition to standard office applications, they offer Zoho Wiki, Zoho Projects, Zoho CRM and Zoho planner. I'm going to come back and spend some quality time with this, and I'll let you know what I discover.
Here's another one I haven't tried. Outlaw says he likes it because of the built-in chat feature, but I find that external chat (like AIM) works fine. And it's free.
Personal Finance: Mint
I've heard good things about this, but my wife does all our finances, and she has her own systems. Outlaw says it's "like an online version of Quicken." You'll need to be trusting to put all your personal finance info online, however. Personally, I would rather use an installed app, then back up the data.
To Do List: I Want Sandy
I use I Want Sandy every day, but it's a mixed bag for me. You send e-mail to the special address they give you, and top the note with "remind me in one week" or something like that. Sandy's computers read that, then do as requested. The biggest beef I have with it is that the e-mails are hard to read. I have to spend five seconds hunting for the item I asked Sandy to remind of, which is always buried in needless I Want Sandy blather. I Want Sandy to fix this, and put my content in an easy-to-spot location in the e-mails. For my real to do list -- and a bunch of other lists -- I use Gubb. If you're unfamiliar with this free list management services, give it a try. You'll be hooked.
Photo Editing: Picnik
I use Photoshop, and can't imagine going online for photo editing. This is another task that doesn't fit into the definition of "work" for most of us, and also something that doesn't need to be done online, unless you're using someone else's computer.
Whether you're working from the beach in Costa Rica, travel on business or just want to set yourself up to be able to work from wherever you please, it's a good idea to make a list of the applications you'll need, then do your own trial-and-error to find the online apps that will suit you best.
I'm interested in your input on all this. What are you using/loving/hating in the online application space?