50mm, as fast as you can afford. - Evan Travers

just out of curiosity...why a prime? you'll be limiting yourself yet again. - Carlos Ayala

Yeah, if you are doing a lot of indoor shots, any of the 50mm primes is a must have. - Scoble, Alex Scoble

Carlos, I was referencing prime as in 'primary lens', not fixed focal length http://en.wikipedia.org/wiki... Basically, a good base lens that I can learn with and add to once I get my sea legs. - FFing Enigma

I'll go against the grain and say the Sigma 30mm. =) 50mm on a crop cam like the XSi doesn't give you "general purpose." It gives you a nice portrait lens. - ronin

And my opinion/recommendation still stands for indoor shooting. - Scoble, Alex Scoble

when discussing glass.....prime will always mean fixed focal. - Carlos Ayala

I agree. My 50mm (Canon EF 50 f/1.8) is excellent, albeit cheap. I use it everywhere I go. I'm also looking at Tamron's 10-24mm and Sigma's 10-20mm wide angle lenses. - Brandon Titus

whats your budget Tina? - Carlos Ayala

No seriously. You should get a prime fixed focal lens. They are clear and relatively cheap. - Evan Travers

I'll be saving up for whatever I wind up getting, so the budget is flexible. - FFing Enigma

then for sea legs, i recommend the 24-105L - Carlos Ayala

If your budget is south of $500 then the Tamron 28-75 gets good recommendations. Kinda lose out on the wide side though. - ronin

I have a 52mm f1.8. It's pretty good. I'm with Carlos here, what made you decide you need a prime? I find my 18-50 gets most of the shooting, even though it's not as pricey as the prime, sometimes I want to get more detail, or more angle. - Will Higgins™

i'd also mention the 24-70 f/2.8 ...but utlimately it depends on what you are shooting and under what conditions. - Carlos Ayala

I love my Sigma 30mm f/1.4 lens, which is what's on my XSi most of the time. Thanks to the cropped sensor, it's almost the same as a 50mm lens on a 35mm sensor. If you do want a prime lens, that is. - Paul Haahr

80-90% of my shooting is outdoors, that's what I enjoy most. Again, I was using the apparently-no-longer-popular meaning of prime aka a primary lens or one that could be used in combination with other lenses in the future. I understand that prime = fixed focal for most people now, and I'm sorry for the confusion. - FFing Enigma

If you've got the cash, then the two that Carlos suggests make for great primary lenses. If you'd rather be a bit less spendy then either the Tamron 17-50 or 28-75 will work just as well depending on whether you want to go wide or long. - ronin

While I would love to have an L series lens (or several), I'm hard pressed to be able to rationalize one, especially with this camera body. Seems kinda like teaching your kid to drive in a lambo =) - FFing Enigma

Have you considered renting some lenses and seeing how they work for you? - τorƍue

I have Tim, but there aren't any places that do so where I live. I would have to rent one/some and have them shipped in which I find off putting for some reason. If someone can recommend a decent mailorder rental place, I'd definitely like to try some out. - FFing Enigma

Getting a prime lens will make you think a little differently about photography. I love my Sigma 30mm f/1.4. Try a bunch of shots at the store; that's what I did. - Rick Cogley