Most of the utilities I use in my day
to day development are open source tools, however one exception to
this is Redgate softwares SQL Compare tool.
Effectively what the tool allows you to do is to compare two SQL Server databases to identify the differences. It will then allow you to choose what changes you want to promote from environment A to environment B and will produce an SQL script to implement the changes.
Using this software, database migrations from DEV -> UAT -> Production now only take a matter of minutes. One thing this software doesn't do is move the data in your tables. Redgate have another tool for that, however I haven't yet used it.
All up this is one of my favourite database tools and is well worth the £245 that it costs. There is also a 14 day free trial you can download if you want to try it (or just have a one off migration to do).
P.S. In case this sounds like a sales pitch I can confirm that I am in no way employed or sponsered by Redgate! I just like the tool.