Question: I have a website in Sharepoint 2007. We use a wsp to deploy our projects. We can deploy dlls, usercontrols, features, but i don't know how to include new lines in the web.config.

Which would be a possible way to make changes in web.config?

Another thing, how can I include resources (resx) in the wsp?

Answer: 
Manually editing the web.config in a multi-server farm is a Bad Idea. Ensuring the web.config files stay in sync on each WFE will become a nightmare quickly.

Using the SPWebConfigModification class to manage web.config changes across the farm is a Good Idea, as changes will be persisted in the SharePoint configuration database, and automatically pushed to every server in the farm.

Having said that, coding against the class can be a pain. Luckily there's a [pretty good front-end](http://spwebconfigmodif.codeplex.com/) that's freely available, giving you a configuration screen in Central Administration to add/remove web.config changes.
there is a very easy way to add safe control entries via Solution. The following snippet added to the manifest.xml will make the relevant modifications to the web.config file. To set other values you should do it in a feature receiver using the [SPWebConfigModification](http://msdn.microsoft.com/en-us/library/microsoft.sharepoint.administration.spwebconfigmodification.aspx) class.

```
<Assemblies>
  <Assembly ...>
     <SafeControl Namespace=".." Assembly="..." Type="..." Safe="True" />
  </Assembly>
  ....
</Assemblies>

```