Well obviously probably slave/black related legislation, but what about other legislation?
Absolutely. This is a point that Richard Bensel makes very persuasively in his book Yankee Leviathan: The Origins of Central State Authority in America, 1859-1877. He points out that Republican congressmen in the 1850s supported measures that would have given the federal government a greater role in promoting economic growth, but these measures were repeatedly defeated by the votes of Southern congressmen. Once the Southerners were removed (or removed themselves), the Republicans had a free hand to pursue these policies.
In particular, these stand out:
The Homestead Act: Northerners since the era of the Free Soil Party had wanted to distribute federal land in the west to eastern settlers free of cost, but had been repeatedly thwarted by Southerners who did not want to upset the even balance between free states and slave states. A version of the Homestead Act had been introduced in Congress in 1860 and was defeated without receiving a single vote of support from Southerners. Once the Civil War began, though, the bill was passed and became law in 1863, giving 160 acres of free land for anyone who would settle and farm in the West.
Transcontinental Railroad: A proposed rail link between the Atlantic and Pacific coasts had been voted down by Congress in 1860, largely because of opposition from Southerners. Once they were removed from the equation, charters were granted to the Union Pacific and Central Pacific companies - which was built between 1863 and 1869.
The tariff: Southern congressmen had long opposed a protective tariff for manufacturers (going back to the Nullification Crisis of 1832-33) because it benefited northeastern industrial interests, while punishing agricultural exporters like themselves. Once the Southern states seceded, though, the Republicans had a free hand to increase tariff rates, which remained high through the rest of the 19th century.
In short, Southern secession gave northern Republicans a free hand to establish a federal government that was more active in the economy, which in turn laid the basis for the rise of Big Business and industrial capitalism after the Civil War.