VB .NET Converter

First, worth to try the VS built in converter.

Another one that looks good, worth a try http://www.aivosto.com/project/vbnet.html - says it works with previous versions and there is trial for small projects.

Microsoft Visual Basic 6.0 Code Advisor can be used on VB6 before converting to VB.NET:
http://msdn.microsoft.com/en-us/vbasic/ms789135.aspx

Finally a couple of more:

http://www.vbto.net/

http://www.vbmigration.com/editions.aspx

Other useful links for migration of VB6 to .NET

http://blogs.msdn.com/ericnel/archive/2008/04/25/visual-basic-6-migration-to-net.aspx
http://msdn.microsoft.com/en-gb/vbrun/ms788233.aspx
http://msdn.microsoft.com/en-gb/dd408373.aspx

Finally here is a promissing link for 5 to 6 but can't follow it at the moment: http://www.topblogarea.com/sitedetails_17682-2.html