Well, under $250 the quality of the lens is obviously not going to match that of the higher priced, and L series Canon Lenses.
Since I am in the UK, I can only guess at US prices, but something like the Canon 55-250mm USM IS lens, which if you have the 18-55mm (kit lens) will compliment it nicely, giving you a total focal range across both your lenses from 18mm to 250mm, which in 35mm terms (1.6x crop factor for 400D) is 28mm to 400mm, which goes from wide angle, to pretty good telephoto.
The IS on the 55-250mm lens will be very useful in either lowlight conditions, when you have the lens zoomed in, or both, on my 210mm I struggle to hand hold exposures of longer than 150th of a second without camera shake, especially if its a windy day!
And to point out, just like Gordon does in his reviews, since the IS is in the lens rather than the body (sensor), then you can see the effects through the viewfinder, which can be very reasuring.
The Canon 55-250mm USM IS is around £250 in the UK, and probably around $400 in the US
IF you simply can't reach the budget for this lens, then unfortunately there is no other lens cheap than this (that I know of anyway) that comes with some type of IS system (sometimes known as IS, VR, OS for different brands of lenses) which makes shooting at the longer focal lengths more difficult, especially in low light!
Other lenses I could perhaps direct you to are:
Sigma 55-200mm f/4-5.6 DC (Canon AF) - £149.99
Sigma 28-300mm f/3.5-6.3 DG Macro (Canon AF) - £229.99
Canon EF55-200mm F4.5/5.6 MK2 USM - £239.99
Canon EF 75-300mm f4/5.6 USM MK3 - £239.99
As to the quality of these lenses, don't expect miricles, they will no doubt have their problems and flaws in comparison to more expensive lenses with higher grade optics, but just like everything else in this world, you get what you pay for
Perhaps some of our more seasoned Canon users would be able to recommend a good lens for you and help you out a little more, but I still say that the Canon 55-250mm USM IS lens is your best bet, and compliments the 18-55mm nicely.
Canon EOS 5DmkII + BG-E6 + Canon EOS 40D + BG-E2N + Canon EOS 33
Canon 17-40 F/4L
USM + Canon 24-70 F/2.8L
USM + Canon 28mm F/1.8 USM + Canon 70-200 F/2.8L
USM IS + Canon 85mm F/1.8 USM
Canon Speedlite 580EX II + Canon Speedlite 540EZ + 2 x Nikon SB-80DX
Cactus V2s Wireless Trigger - 5 x
Cactus V2s Wireless Reciever