...if you've already got VS 2003 that is.
I know many developers sit and watch the VS2005 demos and thing how brillant it all is, and how it's a pain they'll not be using it for x months/years because their employer is so backwards / tight / sceptical. But there's a whole list of things I see in demos time and time again that can be done right now if you know how. Sure, you won't always get the IDE support, and it might not be as well rounded, but if you've only been using vanilla VS2003, then you really want to think about some of the following. Buy me a beer with the cash you save.
Unit Testing: Download NUnit and TestDriven.NET. Note how double-clicking the test failure in TestDriven.NET actually takes you to the failing line, unlike VS2005. Enjoy using NestedTestCase like you can't in Whitbey.
Refactoring and Code Snippets: Download ReSharper and wonder how you ever did without it (or CodeRush + Refactor! if you can't use ReSharper because you're a VB guy)
Nullable Types: Just use those Sql types in the SqlClient namespace, and you're 90% there.
Functional programming / dependency injection: The new generic collections support cute methods to filter the collection (FindAll), where you pass in the filter behaviour as a generic delegate (eg Predicate
Developing without IIS: Write your own webserver, by spinning up a SimpleWorkerRequest and pointing it to a directory full of ASPX files
DebuggerVisualisers: Open that mcee_cs.dat file in (vs)\Common7\Packages\Debugger and you'll know what to do
DebuggerProxies: Refactor the offending class. No excuses.
Strongly-typed config files: Use a XmlSerializerSectionHandler to serialize your .config blocks directly onto settings classes. Retrieve the settings class early (eg Application_OnStart) to get FailFast (sure it's not at compile-time, but...)
Tracepoints: Just use log4net and have that diagnostic stream available all the time, even when the debugger's not attached (you can update the logging configuration on the fly, see...)
Class Designer: Sparx System's EnterpriseArchitect is an excellent UML tool that's not expensive and does a pretty good job (especially compared to how pants Visio is)
Object Test Bench: Write your playing-with-the-class (spiking) code as a unit test. That way, when you've finished playing, you've also written a regression test for the behaviour you're about to use elsewhere.
Master Pages: Either use one of the free reverse-implementations for ASP.Net 1, or use a HTML editing tool that does support templates, like DreamWeaver. While you're at it note that DreamWeaver still beats the pants of the HTML editor in Whitbey, even if the gap is closing.
In-HTML intellisense for anchors etc...: Use a half-decent HTML editor that's got broken link detection (see above)
ObjectBindingSource: It's a little known fact that any object that implements IComponent can already be used as a data binding source in ASP.Net, though it's fiddly to get it on the form unless it's actually Component. I think (total conjecture here) this is what CSLA does.
TwoWayDataBinding: There are existing TwoWayDataBinding implementations for ASP.Net 1 (here's another), that don't require you to subclass all your controls
Operator Overloading (& Continue, using blocks etc...): Use C# :-)
[phew. Did I miss any?]