Some excellent resources are available at the Solution Accelerators Library on TechNet (Solution Accelerators Library)
Ones that may be of interest to the SharePoint Ecosystem are in the Communication & Collaboration area. There are many other solution accelerators that you may find useful as well.
Medium Business Solution for Collaboration Services
This solution provides technical guidance on using Windows SharePoint Services sites to implement company intranet and extranet Web portal sites.
SharePoint Capacity Planning Tool
Performance models for Microsoft Office SharePoint Server (MOSS) 2007 and Windows SharePoint Services (WSS) 3.0 that use the analysis and simulation features of Microsoft System Center Capacity Planner 2007 to help you plan your SharePoint topology.
SharePoint Monitoring Toolkit
Helps you monitor and manage Microsoft SharePoint environments by providing a set of management packs for Windows SharePoint Services 3.0 and Microsoft Office SharePoint Server 2007 (including SP1). These management packs are supported by both System Center Operations Manager 2007 and System Center Essentials.
SharePoint Cross-site Configurator
This tool contains sample code that you can use to automate the deployment of configuration changes across SharePoint site collections as broadly as entire web applications or even entire farms.
Upgrade Toolkit for Windows SharePoint Services Sites and Templates Guide
This solution accelerator provides guidance and tools to enable IT Professionals and WSS users to successfully upgrade their Windows SharePoint Services 2.0 custom sites and templates.