A newer article on this subject has been posted at
Alfresco Cloud cloud is a service from the good people at Alfresco that gives you out of the box alfresco share via a nicely packaged cloud service. And the good news is you can use it for free (with a few limitations)
Sign up for the service
Alfresco cloud offers a free account with 10GiB of storage to use for life. This is a nice place to start testing it out to see if it’s something your business want to pay to use.
Go to http://www.alfresco.com/products/cloud 
Click on Sign up for Free
Enter your email address and click Get Started. You must use a company email, you cannot use yahoo.com email or gmail.
After entering your email, you will get an email from the nice folks at alfresco.
Click on Activate, which takes you to the alfresco site.
Where you enter in your password etc for your account.
Once you have all that done its time to login
Go to https://my.alfresco.com/share/ 
Enter your email address and password and click login
Success you are in!
Let’s give it a test run and try a few things out to see what we can do with it.
The alfresco cloud creates a default site for you with your name in it. Here is my Patrick Bailey’s Home.
Click on it to open it.
Here is this share site. Click on the document Library.
Click on new
Call it MY_TEST and click save
Open up this folder
Drag and drop a few files from your local system to this alfresco folder.
I uploaded a file that was 38MB in size, it took over 7 minutes… a bit slow, but for free can you complain?
Invite a new User to your site
Let’s see if we can invite someone to this alfresco cloud share site.
Click on Invite to Site.
Enter the invitee email, which can be from a yahoo account and select their role.
Here is the email they will receive. Click Accept invitation
They need to now create an account
So adding a user worked just fine, but you can’t add them as a site admin (which is probably a good thing in most cases)
Open a file you added
Click on Share
Rules can be applied to a folder to allow it to do things like start tasks or send emails out when a document is added, updated or deleted from a folder.
To the far right of a folder click on the + button and select Manage Rules.
Click Create Rules
Looking at the actions it looks like you only have a subset of the possible out of the box rules, for example you can’t email.
Here is a screen grab from a home install I have, just to show what you are missing in the alfresco cloud.
See all the additional options that are available?
Folder Rules work, but you have a much smaller set of out of the box options.
Create a new share site
Click On Sites, at the top and then Create Site
Give it a name and click OK
That worked like a charm.
What else can I check....
You can’t customize your site and add blogs, calendars, or a wiki to your site. Personally I am OK with that for this tool. Until this other tools are ready for prime time I do not see a big need for them. So I do not see this feature as a big loss.
Alfreso cloud has fewer dashlets options than a custom install.
Cloud dashlets available.
Custom install dashlets available. Just to show you the difference.
Not a killer for me, there are a few dashlets I do like to use like Web View that would be missed.
You can version documents by hand, but there seems to be no easy way to automate it. There is an easy way to accomplish this with folder rules, but the aspect portion has been removed from the cloud offering so it cannot be done. So long story short versioning has to be done by hand.
You can assign tasks
There are fewer types of tasks you can assign, but more than enough to keep you happy until you really need some customization.
Also I think these two task are named in a less confusing manner than what is available out of the box with a custom install of alfresco
This is a screen shot from Alfresco 4.2 from a custom install. Out of the box there are too many tasks available, also they are too wordy, in my opinion.
There are a few external programs that can be used to access your alfresco cloud or your custom alfresco install. Alfresco Sync, that syncs folders from your alfresco to you own computers folders. Alfresco for the iphone/ipad, which lets you access your alfresco documents via the iphone/ipad
This does not work for the free version of the cloud. In fact I only think it works for enterprise users at this time. L
Alfresco iphone/ipad app
I am not going to go over the setup and use of this program here, I will just say the iphone app works the same with the cloud or with a custom install. Even using the free version of the cloud.
What are the limitations between free and paid?
What are the limitation with this free version?
Looking at their own comparison chart at http://www.alfresco.com/products/compare 
The free version is a very nice place to test and if you have very modest needs may be enough for your small business. You can only store up to 10GiB of information. The largest file size you can have is 50MiB and you have no support.
The Standard version is not a bad deal, for $50 you get 5 users up to 500GiB of storage and a max file size of 2GiB and some support. You also can add a user for $9/mo.
In summary the free version of alfresco cloud is great! It does a lot for free and does not hamstring you from using it effectively. If it works well for you or your business the $50 paid for version is very attractive and may be all you ever need for your small business.
Alfresco cloud also works well with the Alfresco iPhone program!
Even if you require a more custom install to help handle your business document management needs Alfresco cloud is still a good place to get your feet wet before diving into the expense of customization.
 Alfresco Cloud
 Alfresco Cloud login
 Alfresco Cloud Comparison Chart