16. One or more memory devices comprising instructions executable by one or more processors of a topic ranking system, the one or more memory devices comprising: one or more instructions to obtain a list of popular topics, a ranking score for each topic in the list of popular topics, and a topic profile for a particular topic in the list of popular topics; one or more instructions to obtain a user profile that includes categories of topics associated with a user; one or more instructions to determine a personalization score for the particular topic in the list of popular topics, where the personalization score for the particular topic is based on one or more similarities between the user profile and the topic profile for the particular topic, the one or more instructions to determine the personalization score including: one or more instructions to represent the user profile as a first component that represents the user's interest in different subject matter categories, one or more instructions to represent the topic profile as a second component that represents a relevance of the particular topic to the different subject matter categories, one or more instructions to apply a vector similarity function to the first component and the second component to compute a similarity score for the first component and the second component, one or more instructions to apply a transformation function to the similarity score computed based on applying the vector similarity function to the first component and the second component, and one or more instructions to provide, as a boost factor, a numeric value for the personalization score based on a result of applying the transformation function to the similarity score; one or more instructions to assign a revised ranking score for the particular topic in the list of popular topics using the personalization score and the ranking score; and one or more instructions to rank the topics, in the list of popular topics, using the revised ranking score for the particular topic.
16. One or more memory devices comprising instructions executable by one or more processors of a topic ranking system, the one or more memory devices comprising: one or more instructions to obtain a list of popular topics, a ranking score for each topic in the list of popular topics, and a topic profile for a particular topic in the list of popular topics; one or more instructions to obtain a user profile that includes categories of topics associated with a user; one or more instructions to determine a personalization score for the particular topic in the list of popular topics, where the personalization score for the particular topic is based on one or more similarities between the user profile and the topic profile for the particular topic, the one or more instructions to determine the personalization score including: one or more instructions to represent the user profile as a first component that represents the user's interest in different subject matter categories, one or more instructions to represent the topic profile as a second component that represents a relevance of the particular topic to the different subject matter categories, one or more instructions to apply a vector similarity function to the first component and the second component to compute a similarity score for the first component and the second component, one or more instructions to apply a transformation function to the similarity score computed based on applying the vector similarity function to the first component and the second component, and one or more instructions to provide, as a boost factor, a numeric value for the personalization score based on a result of applying the transformation function to the similarity score; one or more instructions to assign a revised ranking score for the particular topic in the list of popular topics using the personalization score and the ranking score; and one or more instructions to rank the topics, in the list of popular topics, using the revised ranking score for the particular topic. 20. The one or more memory devices of claim 16 , where the user profile includes one or more of: information regarding an interest of the user, information regarding documents that the user has accessed, or information regarding one or more services associated with the user.