There's currently three direct ways to transform MJ into EU.
The first is Forestry's Biogenerator, which sadly is grossly inefficient (200,000 MJ becomes 32,000 EU).
The second is Thermal Expansion's Magma Crucible, which (like many things in TE) is on the other end of the spectrum, borderline too good. Using cobblestone from an attached Igneous Extruder, it will convert MJ to EU on a 1:1 basis (20,000 MJ to melt down a piece of cobble, yielding 20,000 EU in a Geothermal Generator). Using Netherrack, you get an incredible 5:1 ratio by reducing the melting cost to 4,000 MJ.
The third is Railcraft's steam turbine. On the downside, it requires a huge upfront investment in steel, and will keep consuming more steel in regular intervals to replace the rotor, but on the upside you get to use Railcraft's overpowered steam boilers to drive it. At the end of the day the advantages and disadvantages cancel each other out and you will convert a pretty balanced 32 MJ/t into 50 EU/t using any solid or liquid fuel you want. One rotor costs 99 steel and is good for roughly 145 to 150 million EU (exact value unknown).