I recently purchased a Canon Xsi and love it. However, I'm getting tired of the kit lens. I borrowed my friends super nice 70-200mm f/2.8 Canon zoom lense which was awesome, but way too expensive for me right now. Since I'm still new to photography I just want a decent, but inexpensive zoom lens. I would probably use it mostly during the day. A fast lens would be nice, but not necessary. At this point I just want something that can bring me in closer than 55mm. Like I said I'm new, so I can't justify spending a ton of money. I did see that Sigma has a nice looking 70-200mm lens similar to the above canon, but its still around $700. I would like to stay around $300 or less. Also, if I can buy a less expensive zoom lens I can probably afford a 50mm f/1.8 Canon lens which I would really like to get as well. Any suggestions?