Below I present my favourite extensions to Visual Studio 2010. Working without them would be much slower and frustrating. This set isn't focused mainly to any of the Visual Studio project type but I've been using them mainly in web development - ASP.NET MVC and WCF projects.
Visual Studio default formatting engine isn't the best solution out there. It is very unefficient when formatting mixed html and C# (Razor). This extension is trying to focus this problem. In my opinion it's definitely better than default engine but in the field of formatting razor views there are still some things to do and fix. But when it comes to formatting pure C# I think we can't find better solution.
Very small extension - it adds one option in solution context menu - when we can collapse all projects in solution. It can spare our time when we have solution with big number of projects inside.
Go To Definition
I've been working a long time with Java and PHP and for these technologies I've mainly used NetBeans IDE. I don't want to start a war which is better Eclipse or NetBeans but I've used to one feature when exploring code in NetBeans: CTRL + click on the identifier is opening definition of a class, interface etc. I don't know why this feature was mapped to F12 in Visual Studio. F12 is far far away from normal hands position - CTRL is better choice for this. This extension is simply adding CTRL + click functionality to the Visual Studio.
When we are looking to code that is indented several times it's hard to tell which ending bracket is matching an opening bracket. This another simple exntesion fixes this problem by adding lines from opening to closing bracket. No more guessing!
There is a best practise saying that code should explaing itself without the need of comments or when you think that something should be commented it's probably been bad written. Whatever the case might be everybody is working from time to time with comments. For quick distinction between code and comments this extension is making them italic. I know this is a little cosmetic change but I prefer it to look like that.
Staying in comments topic they should be written in spoken language so I think they should have a spell checker binded to. This extension is doing this exact thing. I may be a pedantic person but I really don't like typos in ANY text.
VS10x Code Map v2
Making our way through big files (I know that classes with number of methods have bad metrics and etc.) can be frustrating. By default we have a selector with list of methods, fields and properties, but to select something we have to scroll through which isn't effective when we have a long list. Better solution is having this list opened all the time when we simply click one element on the it and we don't need to scroll at all. This extension adds code map window which simplifies exploring code. It has couple of useful configuration options which can help better organize showed code map.
VS10x Method Block Highlighter
Very simple extension which allows us to simply colorize code - it can be helpful when editing code in several places in one file at once.
VSCommands for Visual Studio 2010
The last but definitely not least extension on the list. Frankly speaking my favourite one. I really like "Locate in Solution" feature which is very helpful when we want to locate currently edited file in the solution explorer. I don't like this feature from Visual Studio because we can either turn this on or off - we don't have this on-demand localization - it's really annoying when solution explorer is jumping every time we change a file. Apart from this we can edit project and solution files - which can spare us having another editing tool.
Of course everybody have his or her own best practises and favourite extensions, but I feel comfortable working with mentioned set.