We would like to give our customers access to report bugs and to look at existing bugs and work items, through Team Foundation Server.
For that, we will need a web frontend, which is customer-friendly. It should be easy to use and with a nice UI. I am aware of Web Access, but think it is too developer-oriented for our customers to use.
Is there any good open source or commercial products out there for doing this? It is important that we will be able to customize the products for our needs.
There is WIWA, but it's quite similar to the regular web access tool. It exists more as a licensing aid (helping TFS admins ensure they don't overstep the CAL requirements) than as a fresh new UI aimed at non-developers.
Note: get it from the latest download package for TSWA SP1, not the CTP linked in the blog post
I don't know of any other solutions that are as customizable as you're hoping. I've seen (and contributed to) one-off solutions that were tailored for a specific work item type. At the broadest level, you could say that the bug pages @ connect.microsoft.com and @ Codeplex fall into that category as well. But none of them is publicly available, nor would they be helpful even if published.
You'll probably need to do a one-off of your own using the Work Item Tracking API. Luckily, this is far easier than writing a generalized workflow engine / forms designer that knows how to parse WIT XML.