Larson Learning has two products related to algebra and pre-algebra, called Larson Learning Algebra 1, and Larson Learning Pre-Algebra. These are web-based products for grades 6-9 that feature a lot of voice over explanations and on-screen manipulatives. Larson Learning was previously called SmartMath, but they changed their name when they were acquired by Houghton Mifflin. They also sell two products for elementary-level math, called Larson Elementary Math (Grades K-2) and Larson Learning Grades 3-6.
We were not able to get a demo of either the pre-algebra or algebra products so we can't say much about the look and feel of these products. However, one feature they mention a lot, and that distinguishes Larson Learning from their competitors, is that the teacher is responsible for determining the curriculum of each student. Essentially, the student takes a diagnostic test, which is included with the program, and then based on these results the teacher can include or exclude any lesson from the student's curriculum. Unlike in other programs, such as Aleks, which use the diagnostic test to assemble a suite of targeted lesson modules automatically, in Larson Learning it is used more as a suggestion to the teacher of what the student needs to work on, and the final decision is left up to the teacher.
Larson Learning was one of the four algebra products used in the 2007 Federally funded study by the DOE. In addition they include a lot of information on validation studies that have been done, most of which agree with the industry standard of 5-10% percentile increase on the SAT-9. Interestingly, they also sell an elementary school product and the results from that seem to be in general higher than with their algebra-related products.