You can add an egg and a little bbq sauce to add flavour, and baking your burger on a pan in the oven on a rack lets any extra fat drip out onto the pan, and if you line your pan with aluminum foil it's easy clean up as well.
Also, have you tried ground turkey or ground chicken? They make a wonderful lean burger aswell.
To your ground turkey, add 1 egg, some bread crumbs, onion and garlic, cumin, chili powder, salt & pepper. It's delicious! Serve on a whole wheat bun with fat free mayo, lettuce, ant tomatoe.
Just have fun experimenting with different flavours that you like. Try adding chili powder to your beef, it wil make it a little spicy and taste like chili!