Here's a little tip for you that I've found incredibly useful over the past few months - something that I suspect a lot of you do already.
When I'm involved in a project on which I am implementing SSIS packages I like to keep all packages in a single SSIS-dedicated solution. Typically that solution will contain multiple projects each reflecting a different aspect of the project.
In addition I also like to keep an additional project in that solution called "scratch". Quite simply this is a sandbox area for any of your developers to test out functionality that they are considering adding to their "proper" packages or in some cases I use it to keep packages that demos tricks or best practices. Basically, it can contain anything you like.
The advantage of having a dedicated area for things like this is on many occasions you will require something that is actually in the scratch project. I've even surprised myself by how many times I refer back to the scratch project to grab things that I may have built months and months before and this becomes even more valuable if the scratch project is placed under source control. The only rule I insist upon is that whenever a developer puts a package into the scratch project they prefix the name of the package with their initials.
-Jamie