I thought I would mention a few altenitive forms of sacrifice that are and can be used today, some of which are just as old as the animal sacrifice.
Both the Buddists and Hindus often gave offerings of food sacrifice to the Gods, most commonly was the offering of fruit, though other things might be left as well, such as nuts, seeds, or herbs, plants, flowers, and so forth.
Liquid sacrifce is another a good way to honor and appeal to the Gods, and I have already written a detailed article all about the pouring of libation which is the most common form of liquid sacrifice, but it is not the only method, you can leave in offering a bowl of rain water, or if you have accesses to such, lake, stream, or ocean water would work as well. Milk would make another good liquid offering becasue of its obvious feminine associations and the fact that it is a life giving source.
Something I like to do at times, and can work well is the making of little dolls if you will, just by weaving weads together, they are nothing fancy, or elaborate, really they are the equvilient of stick figures if you will, just weeds bound together to resemeble a head, arms and legs, though you may make yours as extensive or simple as you like, and I will choose a tree in which to leave them under when I wish to appeal to the gods.
Another thing I do which I think makes a good form of sacrifice, is to use/take something of myself this can be anything from something that physcialy comes from me, just as a clipping of my hair, to just something that was in my pocession, a rock I had found and kept in my room, or a clipping of an herb or other plant I have.