... that I don't know where to start!

Blend tool:
XaraX online tutorials
and
Web xealot on blends

Pen tool:
Web xealot on the pen tool

All of Gary's web xealots are fantastic. From page 2 onwards each one is stuffed with XaraX tips and tutorials.
Web xealot main page
Plus he has lots more tutorials and tips if you follow the link to the Xara Xone

Don't forget the help files in the program itself. In XaraX press F1, choose the contents tab then Tools and there are really helpful tips for both tools.

hth
Jessica