Here is list of the stuff I use to make my life easier.  Some of it is free, some is not, but all of it is good.

File Helpers

This is really nice frame work for importing/exporting data.  If you need to pull some records from a text file and shoot them to an sql database this will do it in just a few lines of code.  I have used it on several projects without any issues.  

 http://www.filehelpers.com/

XML Cooktop

I use cooktop when I am testing out xpath statements or build xslt transform scripts.  It is a java program so it kind of runs slow but it works well.

http://www.xmlcooktop.com/

LLBL Gen Pro

LLBL Gen Pro is the best OR mapper I have found out there.  I have been using it since 2005 and have watched it become an awesome product.  I liked it so much I actually purchased a $300 license for use on my home products. 

http://www.llblgen.com/defaultgeneric.aspx

HTML Agility Pack

I just recently came across this and must say it is nice.  I found the need at work to find and replace all class tags in an html document with the actually style info, this is require if you want to send out html emails with CSS styling.  It worked great

http://www.codeplex.com/htmlagilitypack

Liquid XML Studio

I consider this my best find of 2007.  This is a free tool for editing XSD but it is very high quality, most free tools out there do their job well but may be lacking in documentation or UI features, not this one, it is top notch.

http://www.liquid-technologies.com/Product_XmlStudio.aspx

XSQL Suite

Most of my projects require a back end database which is usually MSSQL.  Deploying and managing changes from dev to test to prod is a pain, this tool makes life easier.  I only use the compare tool but I believe they are all good.  There is a free version that only works on SQL Express Database but this tool is worth the money if you deploy changes a lot.

http://www.xsqlsoftware.com/