Every technical focused consultant would like to invent the wheel, but in our project that would be too expensive. Yes, unfortunately we are bound by the budget.
Of course, the use of add-ons saves us lot of time, stress, pizzas and cans of coca cola... (don't like Pepsi). The difficulty is more to find the right add-on for the functionality your customer needs.
The common add-ons from known vendors like c360, Celenia, CWR Mobility are easy to find, but to find add-ons with more specific functionality becomes harder.
The sites I did find and use give an overview of available crm add-ons, usually divided by category:
Please leave more interesting sites in the comments.