I'm blogging about SQL Server Express? Oh my! 
Truth is I would have never done this before...SQL Server 2008 Express
This new version is, in a word, Sweet!
http://blogs.msdn.com/sqlexpress/archive/2008/06/10/sql-server-2008-express-rc0.aspx
This is by far the best Express version yet.
My favorite feature by far is the added ability to Import and Export data to and from Local and Remote SQL Servers.
Just like big brother SQL Server has been able to do all along, but the Express versions had to work with scripts.
Well no longer, you now get total control and I can hardly believe it.
Today I installed SQL Server 2008 Express on my XP Pro SP3 machine to give it a spin.
I'm already using SQL Server 2008 on my Vista box for my Developer Evangelism. (With SQL Server 2005)
Let me warn you, well, let me make a quick note about the requirements on XP if you want to install this.
You will need the latest .NET Framework v3.5, but not the older FX version, the new SP1 3.5 version is what you'll need.
http://www.microsoft.com/downloads/details.aspx?FamilyID=8c36aca4-e947-4760-9b05-93cac04c6f87
You'll also need to install Windows Installer 4.5, don't even try to install SQL 2008 Express without this, won't work.
http://www.microsoft.com/downloads/details.aspx?FamilyID=5a58b56f-60b6-4412-95b9-54d056d6f9f4
Finally you'll need to install Windows PowerShell 1.0, odd but true, SQL Server 2008 Express needs it, even on XP.
http://www.microsoft.com/windowsserver2003/technologies/management/powershell/download.mspx
If you get stuck please try the forums:
http://forums.microsoft.com/MSDN/ShowForum.aspx?ForumID=1621&SiteID=1
Everything has changed in SQL Server 2008 and the Express version installs just like big brother.
With the exception of the Product ID, the Express setup will enter an Express FREE PID for you. Nice.
When you get to the User credentials section of the Install process for the Engine you may get stuck, it's all new and a bit confusing.
On Vista you can type "N" in each edit box and you'll be given choices to pick from.
For XP I had to use the dropdown option for each editbox, but it still allowed me to choose the account I wanted to use. Handy
If you have trouble with the .NET Framework on XP I'd recommend un-installing v3.0 and v3.5 then reinstalling from the link above.
This version of SQL Express is very large, over 500MB. (For the advanced features version.)
Allow yourself a few hours to get this downloaded and installed.
In the end you'll be very happy with the best SQL Express yet.
UPDATE: Received a little feedback from Mike Wachal on the SQL Server Express team:
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Hey Mark,
Great post and great to see that you're happy with SQL Express.
I'm forwarding your comments to the team that did the work to put Input/Export into Express so they feel the love!
I notice from the size you mention that you're using SQL Express with Advanced Services.
It might be worth pointing out to the home viewers that there are actually two editions of Express: SQL Express and SQL Express with Advanced Services.
The core SQL Express is smaller and doesn't require PowerShell before installing, but it also doesn't have Management Stuido, BIDS or Reporting Services.
(It does have the I/E Wizard though)
If all you need is the core db engine - this is a smaller alternative.
Thanks for the kind words,
Mike Wachal
SQL Express team
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Thanks Mike! 
Note: DiscountASP.NET is testing SQL Server 2008 and will be adding it for Developer accounts soon.
If your ready to try IIS7 / Windows Server 2008 and need an honest incentive...
Go to https://www.discountasp.net/signup
Use this promotion code: WISEMX
(You'll get an entire year for the price of just 6 months.)
I promise to help you with whatever is needed, I'll be there for ya. 
Salute,
Mark Wisecarver
Technical Evangelist for http://DiscountASP.NET
Note: I am not paid for my endorsements or for my Developer Evangelism.