[sphinx]

Admin CP -> Templates -> Modify -> [expand list] -> Forum Home Page Templates -> forumhome_forumbit_level....

for the category bars that contain just the category text it's going to be the forumhome_forumbit_level1_nopost template (or maybe it's level2).
it should be the align="center" in line one that should do the job it worked fine for me

<tr id="cat">
<td bgcolor="{categorybackcolor}" colspan="6" align="center"><a href="forumdisplay.php?s=$session[sessionhash]&forumid=$forum[forumid]"><normalfont color="{categoryfontcolor}"><b>$forum[title]</b></normalfont></a>
<br><smallfont color="{categoryfontcolor}">$forum[description]</smallfont></td>
</tr>