Hi,
Welcome to the forum! If your on a budget and not considering any of Canon's prestigious L series lenses just yet then I can recommend Sigma as a brand as well as Tokina.
If your into landscape and general portraiture then there are plenty to choose from. I have recently had the Sigma 30mm f/1.4 and its really great, wide enough for groups of people, landscapes and also very satisfactory for single portraits too. All in all great bit of gear.
Around at £193.99 from:
http://www.onestop-digital.com/catalog/product_info.php?cPath=24_28&products_id=122
It is a prime lens (meaning no zoom basically), but the quality is fantastic for the price.
One stop is based in Hong Kong but don't let that arouse suspicion, they are great! Lots of members have bought from them and always had great service.
As for zooms, it may be an idea to save up for a good zoom lens that you won't get disappointed with a while after owning it. The Canon 70-200mm f/4L is a very good lens but it maybe more than you want to spend right now.
I have made the mistake of buying gear too cheap in the past and although it's alot of money to consider for the better quality stuff, in the long term you will end spending less. just my opinion though. I'm sure there will be someone along that will also share some helpful advice and opinions.
Anyhoo,
Here's some images I have taken using the 30mm f/1.4
All the best and be sure to post your pictures too!