Adding some skills to the list in LotFP seems to be a popular choice, especially for broadening the scope of the Specialist class. I’ve made some changes myself; I’ve removed one skill, and replaced it with three new ones as well as a loose guideline for adding a secondary skill.
I’ve also made a class revision, which I will present in more detail later, and a part of this revision means that classes other than the specialist get a few skill points as the level (though they have to choose where to spend them based on a restricted class list, while the specialist is still able to increase all skills). These new skills are an attempt to both make specialists able to fill more roles, and to present a couple of skills that can be interesting for other classes.
First, the skill that had to go:
Open Doors is, to me, not a skill but a test of strength. You can apply strength bonus to the test, get help and use suitable tools, but I don’t agree with the fact that you can actually spend skill points to learn how to do this better; the task just feels too basic.
Now, for the three new ones:
Lore governs the characters knowledge of most learned subjects, and presents a way for me to introduce some background information into the game. It supplies a lot of flavor, but players can also use it in a number of mechanically relevant ways; it can be used to make rough “identifications” of magical items in the field, such as sipping a potion and testing a weapon. Nothing like an Identify spell, of course, but at least some basics.
Medicine lets a character perform some basic first aid in the field, as well as function as a physician to improve the recovery of fellow characters during downtime.
Riding is for those characters who want their horse (or steed) to be more than a mode of transportation; fighting on horseback, mainly, or riding something other than a horse.
Lastly, characters can take a secondary skill to encompass most anything they want. These are mostly for flavor, however, and must obey two simple rules; they cannot overlap with any of the existing skills, and they must have a narrower scope. Blacksmithing is an excellent secondary skill, “perception” is not.
I’ve created more in-depth rules for these skills, including a closer definition of how and when they are used as well as some lists with situational modifiers – you can find them in this PDF or in the Library.