Tombow Mono Professional Drawing Pencils
were previously very hard to locate. I had to order them from an online animator's supply store. DickBlick now carries them - hooray! Buy them in quantity, because I'm sure you will absolutely love them like I do!If they ever stop making these, I'll break down and actually cry. They are that good.

Prismacolor Verithin Pencils
have harder leads than regular Prismacolor colored pencils and are non-toxic, blend-able and erasable. I really like these. You can get the smaller assortments and then later add colors, but you will spend about 75 cents to a dollar for each pencil, so it's more economical in the long run to just go for the larger assortments.
Prismacolor Colored Pencils are the most popular in the United States for good reason. They are very vibrant, have a wonderful range of colors, are non toxic, and have a smooth and creamy blending consistency. Downside? They're non-erasable. They are waxy. If you make a mistake, you might be able to carefully scrape away some of the pencil, but that's it. I use a 'test paper' of the same type and shade as the portrait I'm working on, to pretest pencil blends before committing them to the final artwork.

You might also be interested in a colorless blender pencil (shown above.) When you overlay colors and want to blend them even more than a blending stump can do, give these a try. I have found that when I do colored pencil portraits on a colored matboard, the blenders can really help give the colored pencil a blended pastel quality. Something to watch for when using the blenders is that there can be some inadvertant transfer of colors - if you are working on something red, for example - and then you work on a yellow area, some of the red may still be on the tip and ruin your yellow. Rubbing it on some paper or wiping it usually helps avoid this problem. I have tried the blender markers and didn't find them very useful (were kind of messy and I didn't like the vapor it gave off).
I recently purchased a set of these Lyra Skintone Giant Pencils and they are wonderful. Definitely a lot of fun, but I haven't used them for a portrait yet. This set of pencils mimics the most popular skintones, and the pencils have a wonderful consistency. Mechanical Pencils
I find that a good mechanical pencil is indispensable for fine detail areas like eyelashes, eybrows, parts of jewelry, etc. Go ahead and get a good quality one like Alvin Draft/Tec Pencilsor Staedtler-Mars. They should last you for years, and the leads aren't expensive to buy at all either! Most of my earlier artworks were nearly all done in mechanical pencil.