I bought Beersmith. You can set up your own equipment profile, there are thousands of recipes online and the software will automatically scale any recipe to your profile. It will also convert from extract to all grain and vice versa.
You're not going to find a lot of made to order kits for 2.5 gallon - almost all are 5 or 1 gallon. Fortunately scaling a 5 gallon recipe is as simple as cutting it in half. You can take any of the 5 gallon recipes and half them and then just buy the ingredients separately (Northern brewer for example lists their kit ingredients right on the site, or you can go the recipe section on the forum).