In Sharepoint 2010 OOB, it looks like you can create forms that do full CRUD (create, read, update, delete) of SQL Server tables without programming. There are a series of videos that can give you a pretty good idea of how that is done.
OOB sharepoint foundation 2010 seems to have the following limitations:
- Only tables (in Sharepoint speak Office item-types) that were anticipated by Sharepoint are supported OOB (contacts, tasks, calendars...)
- Subforms are not supported.
- It seems like only one table and no relationships can be worked with period. So no combo-boxes populated by queries.
Sharepoint Enterprise 2010 seems like it supports subforms and the possibility of handling table relations (in sharepoint speak "associations") in a rich manner without coding. You can get a sense of what's possible from this video.
For rich forms without coding, the answer seems like it should be Access Services on Sharepoint. However, Access Services can't use Sharepoint's Business Connectivity Services (BCS) to connect to a SQL Backend. In other words, Access Services cannot connect to SQL Server. See this MSDN communit post for what seems like a conclusive statement about this limitation of Access Services.
I do not know whether the SQL backend data can be searched using the Sharepoint interface.