12. A system comprising: one or more computers including: a search interface configured to: receive, from a user device, a first search query during a current search session, the first search query comprising one or more first query terms; receive, from the user device, an additional search query during the current search session, the additional search query comprising one or more additional query terms and the additional search query being received subsequent to search results for the first search query being provided in response to the first search query; and a session-based search query suggestion module configured to: store search queries included in a current search session to a session data store and to a query log, organize previous search queries in the query log into a set of previous search sessions based on associations between the previous search queries, each previous search session having concluded prior to the current search session; identify a similar subset of previous search sessions from the set of previous search sessions, each individual previous search session of the similar subset being identified for inclusion in the similar subset based on the individual previous search session being a search session during which the first search query and the additional search query were both received, the similar subset lacking at least one previous search session of the set of previous search sessions; identify, from the similar subset of previous search sessions, a set of follow-up search queries, each follow-up search query being a search query that was received subsequent to receipt of the first search query and the additional search query in at least one of the previous search sessions of the similar subset; identify, for each follow-up search query, a frequency at which the follow-up search query was received in previous search sessions subsequent to receipt of the first search query and the additional search query; aggregate the set of follow-up search queries from the similar subset of previous search sessions; select, from the aggregated follow-up search queries and based on the identified frequencies that have the highest frequency of occurrence, a suggested search query for presentation in response to receipt of the additional search query during the current search session; wherein the search interface is configured to receive the suggested search query and to provide the suggested search query with search results for the additional search query to the user.
12. A system comprising: one or more computers including: a search interface configured to: receive, from a user device, a first search query during a current search session, the first search query comprising one or more first query terms; receive, from the user device, an additional search query during the current search session, the additional search query comprising one or more additional query terms and the additional search query being received subsequent to search results for the first search query being provided in response to the first search query; and a session-based search query suggestion module configured to: store search queries included in a current search session to a session data store and to a query log, organize previous search queries in the query log into a set of previous search sessions based on associations between the previous search queries, each previous search session having concluded prior to the current search session; identify a similar subset of previous search sessions from the set of previous search sessions, each individual previous search session of the similar subset being identified for inclusion in the similar subset based on the individual previous search session being a search session during which the first search query and the additional search query were both received, the similar subset lacking at least one previous search session of the set of previous search sessions; identify, from the similar subset of previous search sessions, a set of follow-up search queries, each follow-up search query being a search query that was received subsequent to receipt of the first search query and the additional search query in at least one of the previous search sessions of the similar subset; identify, for each follow-up search query, a frequency at which the follow-up search query was received in previous search sessions subsequent to receipt of the first search query and the additional search query; aggregate the set of follow-up search queries from the similar subset of previous search sessions; select, from the aggregated follow-up search queries and based on the identified frequencies that have the highest frequency of occurrence, a suggested search query for presentation in response to receipt of the additional search query during the current search session; wherein the search interface is configured to receive the suggested search query and to provide the suggested search query with search results for the additional search query to the user. 15. The system of claim 12 , wherein the suggested search query comprises multiple suggested search queries.