dd-wrt runs on a lot of stuff "At the moment DD-WRT supports more than 80 different router models", it's based on chipset compatibility.
Supported Devices - DD-WRT Wiki I have it running on a wrt54g v4 (linux based) and also on a wrt310n (pos no jumbo frames on a gigabit switch) the wrt54g v5 is a beast of it's own. Basically they cheaped out trying to lower the cost of manufacturing and really ruined a good thing for us. The v6/7/8 are flashable, but with much more work. I had a v8 working but then it randomly broke 6 months later, exchanged it for the 310n. Have to say I haven't used tomato, but i'm happy with DD-WRT.