It is no secret that off-contract smartphones are increasing in popularity; with decreasing prices and new players getting in the game, what seemed like a passing whim will surely become a trend soon enough.

Minor carriers like Boost and Virgin Mobile are becoming stronger by the day, and, although we don’t see them threatening Verizon, AT&T, Sprint and T-Mobile anytime soon, their market shares are definitely going up.

But if for some reason Boost and Virgin’s offers failed to convince you until now, the next days seem like the ideal moment to go from postpaid to prepaid, courtesy of a “yard sale” organized in collaboration with RadioShack. Three HTC phones are offered for heavily discounted prices through the retailer, while two other new handhelds from ZTE and Samsung have launched with RadioShack on the cheap.

The EVO V 4G for Virgin Mobile is probably the most enticing phone on sale, going for $229.99 after a $70 (23%) discount. This is not exactly a brand new handheld, but it does run Android 4.0 ICS with HTC Sense UI 3.6.

Sporting a 4.3-inch qHD (960 x 540) display, the EVO V comes rocking a 1.2 GHz dual-core Snapdragon S3 processor and 1 GB of RAM. Known as the EVO 3D back when it was sold by Sprint, this little guy comes with a glasses-free 3D screen, and a 5 MP rear-facing shooter with 3D capabilities.

The second HTC phone on sale via RadioShack is the EVO Design 4G for Boost Mobile. This is also up for grabs for $229.99 after a $70 discount, but unfortunately it is already out of stock online. You should still have no problem finding it in stores, although we don’t know why you’d choose this over the EVO V.

The EVO Design has a smaller 4-inch screen with the same 960 x 540 display, is powered by a slower 1.2 GHz single-core processor and also comes with less RAM (768 MB).

Last, but not least in HTC’s line-up is the “chintastic” One V for Virgin Mobile. This is also out of stock online, but it certainly makes it worth a trip to your local RadioShack store, as it’s available for just $149.99 after a $50 discount.

The 3.7-inch capacitive display with 800 x 480 pixels resolution and the single-core 1 GHz processor might not sound very hot, but the ICS, 5 MP camera and Beats Audio sound enhancement are certainly not standard features for $150 phones.

All three HTC phones will get back to their usual prices once the RadioShack promotion ends, so you only have until September 29 to decide which one of the trio is the best fit for you.

If HTC’s not your favorite brand, you have two other attractive options from ZTE and Samsung. The brand new Warp Sequent and the Galaxy Rush were until now only up for grabs via Boost Mobile, but starting today they can be purchased through RadioShack brick and mortar stores too.

RadioShack is offering the ZTE Warp Sequent for $199.99, while the Samsung Galaxy Rush is available for $149.99. You can get the two phones from Boost at the exact same prices, so there’s no deal going on here, although it’s always nice to have more options.

So, what say you, folks? Will you be taking advantage of RadioShack and HTC’s exclusive deal? Do the Warp Sequent or Galaxy Rush sound more attractive?