I found a really helpful article on the Silverlight forums answering a question I've been wondering about. As some of you may know, you can author cool controls in Expression Design that use Live Effects. You may spend much of your time developing Silverlight applications in Blend, but the kicker is that currently you cannot author live effects in Blend.
The workaround is shown here.
"In Expression Design, follow these steps:
1. Create your object with effects
2. File > Export > Save as type > XAML
3. In the Export XAML window, Select Silverlight (under Document format) and Rasterize live effects (under Effects).
Note: Rasterizing live effects creates a folder with the same name as your XAML file (appended with _files) and inside is a single file called image0.png. You'll need this folder later. The default location is C:\Documents and Settings\username\My Documents\Expression\Expression Design.
In Expression Blend, follow these steps:
1. Project > Add Existing Item
2. Select the XAML file you created in Design and click Open
3. With Windows Explorer, go to the folder where you originally saved the XAML file, copy the corresponding folder (see note above), and paste it into your Silverlight project folder (default location C:\Documents and Settings\username\My Documents\Expression\Expression Blend Projects\projectname).
4. In Blend, on the Project Files list on the right, right-click your XAML file and select Open
Note: If you see an error message when your XAML window opens instead of your image, you may have put your *_files folder in the wrong project folder.
5. Select and copy your image object
6. Open the Page.xaml Design window and paste your image object (just click OK when the error dialog window appears)
7. Open the Page.xaml XAML window and change the \ in the image source path to /
8. Press F5 and view your image, with effects, in your Web browser!"
Easy. I'm sure that Live Effects will be coming soon to Blend (don't quote me on that because I have no idea) but for the time being, this is the workaround to do it.