Time after time, i have been forgetting this wordpress. You will know how important it is to output a category name in index page or in the blog post page (single.php)
Here are the 2 easy ways to output the category name.
Dont forget that this code will only work, only within the post loop.
1. Category with hyperlink
<?php the_category(', ') ?>
This will print ALL categories, separated by commas. If you want to change to another separator, you can replace the comma.
2. First Category Name
<?php $cat = get_the_category($post->id); echo $cat[0]->cat_name; ?>
This code will output only one category name.
Hope this small tip on wordpress code, helps!