First and foremost, I would recommend getting one of the "Applied .NET
Framework Programming" books by Jeffrey Richter.  I think there are now
three versions of basically the same text.

http://tinyurl.com/94bes

It is neither "Learn to Program" nor an all-encompassing "Reference" book.
However, the in-depth explanation, in simple language, of core .NET
functions that you will use daily make this book a MUST (IMHO).

Next, I would you and your friends to force yourselfs to do everything in C#
from now on.  If that is not possible, then make sure everyone who will be
using Visual Basic .NET turns Option Explicit ON and Option Strict ON by
default in the IDE options.  This will result in all of you needing to
familiarize yourselves with "DirectCast" on day one (if you use VB.NET).

The next book I would recommend, assuming Visual Basic.NET, is Dan Clark's
"An Introduction to Object-Oriented Programming with Visual Basic .NET".

http://tinyurl.com/exocg

One of the worst places to start learning programming in the .NET Framework
is sitting in front of the IDE typing in code.  Dan's book spends the first
few chapters giving you an introduction to creating a Software Requirements
Specification, Use Cases, Activity Diagrams, Sequence Diagrams, Class
Diagrams, and other very helpful aspects of UML.

Finally, I can recommend Mike Gunderloy's "Coder to Developer: Tools and
Strategies for Delivering Your Software".

http://tinyurl.com/9sgrz

I found this book to be very helpful at the point in my career when I bought
it.  I admit that your mileage may vary depending on where you are in yours.

Good Luck,

Carl

I would recommend:

Object-Oriented Analysis and Design with Applications (2nd Edition)
by Grady Booch

--
EventStudio 2.5 - http://www.EventHelix.com/EventStudio
Generate Sequence Diagrams in PDF and Word EMF from plain text input

I'm going to add to the excellent recommendations made so far with two books
that will make a huge difference.

For naming conventions, structures, and version control issues: "Code
Complete" by McConnell
For OO software development, patterns, and understanding how to really "get"
OO software development: "Design Patterns Explained" by Shalloway and Trott.

I often hand out copies of the latter book to folks who want to take that
next step to becoming a designer instead of just a coder.

HTH,