The easiest way to do this is to use the search functionality built into Team System Web Access (TSWA). This uses the SQL Server Fulltext search engine in the back-end. This will find all matches of the string in not just the title of the work item, but the description as well.
One of the questions I've seen a few times now about this functionality is "Where is it??". This is because the search box looks disabled, so people tend to overlook it.
Now it's even easier to search for work items with the advanced search syntax. Similar to Outlook search syntax, you can reference any work item field by either using the field name, or by using some shortcuts.
Here's a simple search example that searches for resolved bugs assigned to me which contain the word "northwind" in the Title or Description.:
northwind a=@me s=resolved t=bug
Another way to quickly search work items within Visual Studio is to use Corneliu's TFS Quick Search Addin for Visual Studio. It reflects over the .NET controls and searches for the string that you type in. This means that it will only work for fields that are visible in your query. It's very quick at doing that though.