So: it's the first Monday in May, your company just signed up with Salesforce.com, and you — yes, you — are The Chosen One: you get to bring all the magic to life for your organization. (Warning: that link includes an overscored soundtrack which will I repeat will disturb any nearby co-workers.)
Well, congratulations and welcome. You're in the right place and, if you're like most people, you'll like being here. The Force.com platform — that's the part of the salesforce.com app that lets you build exactly the functionality you need — is a powerful tool that's got a lot going for it.
Your first step is to head over to the technical library and get to know to app at a beginner's level. I recommend the workbook. It's a bunch of quick lessons that give you a broad overview of the platform and what it can do, and it will help you get your dev environment up and running.
Once you've gone through that, you're probably going to want to see a number of real world examples, and that's why I'm writing this article: to help you find some powerful, popular and open source real world examples that will make your job easier.
Check out Force.com Labs (who, incidently, you might want to follow as @ForceDotComLabs on Twitter as well). There are more than 250 apps available, probably one that will help you get started on your app.
The second is to take a deep dive into the many open source projects surrounding the Force.com ecosystem. There's a complete list over on Code Share, but I'd like to highlight a few that I'm familiar with since I work on them. BONUS: These are active projects, all of which accept contributions. Working in these apps is a great way to hone your development skills — so please jump right in.
Chances are someone in your organization will come to you in the near future and say "Can we track projects in Salesforce?" Yes! And Milestones PM is the way to do it. It includes great examples of robust Apex triggers, both simple and complex Visualforce pages, and examples of exchanging data using XML. You can browse the source code over on GitHub.
Finally, you will very likely come to a use case that requires object scoring (maybe Leads, maybe something else). Lead Scoring is a great app that shows how to manage and execute scoring algorithms in a highly dynamic, user configurable way. Again, the source code is over on — you guessed it — GitHub.
On the subject of GitHub, if you're new to it, don't panic: I've put together a guide that shows you how to use it with the Force.com IDE and these Force.com Labs apps. See the post "How to use Git, GitHub and the Force.com IDE".
I would be remiss if I didn't take a moment to introduce other open source projects you might benefit from checking out. For examples, the good folks over at DeveloperForce have a fantastic GitHub account feature toolkits for iOS, PHP, C# and many, many other languages. There's also a really interesting GitHub account called ForceDotCom which features code from some of our very excellent R&D team.