The SQL Server 2005 and SQL Server 2008 product family has quite a few editions now, so what does this mean for SQL Server Integration Services? Starting from the bottom we have the free edition known as Express, and the entry level Workgroup edition, as well as the new Web edition. None of these three include the full SSIS product, but they do all include the SQL Server Import and Export Wizard, with access to basic data sources but nothing more, so for simple loading and extraction of data this should suffice. You will not be able to build packages though, this is just a one shot deal aimed at using the wizard on an ad-hoc basis.
To get the full power of Integration Services you need to start with Standard edition. This includes the BI Development Studio, for building your own packages, and fully functional IDE integrated into Visual Studio. (You get the full VS 2005/2008 IDE with the product). All core functions will be available but with a restricted set of transformations and tasks. The SQL Server 2005 Features Comparison or Features Supported by the Editions of SQL Server 2008 describes standard edition as having basic transforms, compared to Enterprise which includes the advanced transforms. I think basic is a little harsh considering the power you get with Standard, but the advanced covers the truly ground-breaking capabilities of data mining, text mining and cleansing or fuzzy transforms. The power of performing these operations within your ETL pipeline should not be underestimated, but not all processes will require these capabilities, so it seems like a reasonable delineation.
Thankfully there are no feature limitations or artificial governors within Standard compared to Enterprise. The same control flow and data flow engines underpin both editions, with the same configuration and deployment options allowing you to work seamlessly between environments and editions if using the common components. In fact there are no govenors at all in SSIS, so whilst the SQL Database engine is limited to 4 CPUs in Standard edition, SSIS is only limited by the base operating system.
The advanced transforms only available with Enterprise edition:
Data Mining Training Destination
Data Mining Query Component
Fuzzy Grouping
Fuzzy Lookup
Term Extraction
Term Lookup
Dimension Processing Destination
Partition Processing Destination
The advanced tasks only available with Enterprise edition:
Data Mining Query Task
So in summary, if you want SQL Server Integration Services, you need SQL Server Standard edition, and for the more advanced tasks and transforms you need SQL Server Enterprise edition.
To recap, the answer to the often asked question is no, SQL Server Integration Services is not available in SQL Server Express or Workgroup editions.