Maybe you were tasked to provide certain functionality for your SharePoint 2007 instance? Maybe windows workflow foundation doesn't cut it? Or you just need a simpler solution?
Event Handlers might be an answer that you're looking for!
For those of you that don't know what an Event Handler is here's the Wikipedia Definition:
"In computer programming, an event handler is an asynchronous callback subroutine that handles inputs received in a program. Each event is a piece of application-level information from the underlying framework, typically the GUI toolkit. GUI events include key presses, mouse movement, action selections, and timers expiring. On a lower level, events can represent availability of new data for reading a file or network stream. Event handlers are a central concept in event-driven programming.
The events are created by the framework based on interpreting lower-level inputs, which may be lower-level events themselves. For example, mouse movements and clicks are interpreted as menu selections. The events initially originate from actions on the operating system level, such as interrupts generated by hardware devices, software interrupt instructions, or state changes in polling. On this level, interrupt handlers and signal handlers correspond to event handlers.
Created events are first processed by an event dispatcher within the framework. It typically manages the associations between events and event handlers, and may queue event handlers or events for later processing. Event dispatchers may call event handlers directly, or wait for events to be dequeued with information about the handler to be executed."
In case of dealing with WSS 3.0 Event Handlers all you need is the following:
1. Brian Wilson's EventHandlerSolutionStarterKit, is a great template solution that you can use to build all your own event handlers, and is a must whether you're a n00b (beginner) or well experienced, well I still use it. Brian coupled his solution with the Sharepoint packaging solution from http://blog.thekid.me.uk so that you can build and deploy .wsp files straight away.
2. Once you code your event handler you should then proceed to get (again Brian's) SPSCustomAdmin to make the deployment of your event handler far less painful that it should be.
3. If you're still stuck on coding than maybe you should check out some common and simple coding tasks from Ishai Sagi.
4. Remember that you're dealing with synchronous and asynchronous events. The ones that end with "ed" like Added are asynchronous and they happen after the event and the ones that end with "ing" Adding are synchronous and they happen when the event happens and should be a bit lighter on the resources (take this one from me).
5. If you're dealing with synchronous events bear in mind this article, again from Ishai Sagi (follow the links for further explanation).
Make yourself very familiar with the WSS 3.0 Object Model and the world is your oyster when it comes to SharePoint Event Handlers.
This is all you need, but if you need any further help please don't hesitate to contact me.