Tortoise CVS is by far the best product.  It is a well supported open source product that is freely available. Its one serious drawback is that it only integrates with Windows Explorer. So it does not integrate with Visual Studio.

There was an open source project to create a Visual Studio plug-in for Tortoise CVS. It was imaginatively named SCC plug-in for TortoiseCVS. This project never made it out of Alpha. The last message posted to the site in 2004 says “Regrettably, the quality of this project is still very low, making it unfit for general use.”

Jalindi Igloo is a plug-in created by an individual developer, Graham Robertson. It is a beta product that has not been updated since 2002.

TamTam CVS SCC is a functional and current plug-in that integrates CVSNT with Visual Studio. It was developed by and is maintained by an individual developer, David Levinson. It costs $4.99 per user.

CVS Suite provides a CVS plug-in for Visual Studio. It is owned by March Hare Software Limited which has offices in the US, Australia and Europe. I requested a trial version of their software to test and they told me they do not create trial software. They recommended that I purchase a single user license for $150 in order to evaluate their product. So I have not tested this product.

I found a reference to EasyCVS but there web site does not appear to exist any more.

The only product I can recommend is Tortoise CVS. Unfortunately, it does not integrate CVS with Visual Studio.