(Rating: 4 out of 5)
List Integrity Web part by Bamboo Solutions is one of those controls I have used to solve specific parent/child relationship issues I had in the past. If you don't have the time to develop a simple way to execute relationships between lists this might be something you want to look at.
I would classify this Web part as almost a developer tool, as it creates relationships (via id's) between multiple lists using specially designed columns. The business value here is that you don't need to develop this functionality yourself. One of those big difficulties you run into in SharePoint consistently is its lack of any meaningful Parent-Child Relationship functionality and this tool really helps fill some of that gap that lookup columns and the loose relationships of SharePoint data cannot.
To provide a better example of how this can be used effectively here is a simple scenario. Let’s assume I have to create a really basic CRM style concept of accounts with opportunities. We get this all the time where we need a simple parent/child relationship with SharePoint lists.
With Bamboo's solution, at a very low cost, we can achieve the example shown below. This took me literally 10 minutes to build and take the images. Think of the difference between that and at minimum several hours of development time.
For me personally, and many of you out there, I would rather have my developers working on the powerful things we will do once these lists are connected, rather than spend their time on the connection.
The tool is relatively simple, works for the same or different sites, highly reusable and applicable to many scenarios. Its flows include read-only views of information, cannot have TWO lists showing on the same page with the Bamboo Link column type - Will result in duplicate links, and it can only show list data in child list forms, so the parent child relationship is almost '1 way' in a sense.
I would recommend trying the trial out and seeing if this product meets your needs, I know it did for me.