All of them are potentially correct. The difference in meaning is subtle and not always definite.
The first example has the verb in question in the simple past. The second in the present perfect. In this context, the two cover a range of situations that have a lot of overlap. Either could be used for a project that you are no longer working on. Either could be used where you are still working on some project(s), or where you are not, though the first would fit more naturally in the case where you no longer work on projects, or at least projects of the same nature. The simple past seems more natural where there's a disconnect - like if you're not longer a software developer, and talking about projects you worked on when you were. However, there's no hard and fast rule here, and there's no good reason to easily explain why either fits more in one situation than another.
The third is the present perfect progressive. It carries the closest association with a project that you are still working on, but it could also fit where you are still working on one or more projects other than the one in question. If you no longer work on the same sort of project (like you're a former software developer, and the projects in question are software), that would not feel entirely appropriate.
Some of this shading of meaning is because you are talking about "one of the most interesting projects", and thus the verb may be seen as referring to the projects, not to the one of. The meanings would shift significantly if it were "the most interesting project", and differently if it were "the most interesting of the projects", and different again for "one of the most interest of the projects".