(CNN) -- With Thursday's release of the iPhone 4 on Verizon Wireless, now is a pretty good time to buy a cell phone.
Whether or not you want an Apple phone, cellular carriers are sweetening their deals in the hopes of luring new customers or, at the very least, holding onto the ones they already have.
AT&T Mobility added an attractive new calling plan and is offering some phones for a penny with a two-year contract. This weekend, T-Mobile is flatly giving away every phone in its catalog -- again, only to people willing to sign contracts.
AT&T began offering a program on Thursday that grants customers unlimited calling time when talking to someone who's also on a cell phone. The plan, called Mobile to Any Mobile, is included with AT&T's unlimited text messaging plan, which costs $20 extra per month.
AT&T is also promoting a Super Smartphone Sale, in which the carrier is selling a BlackBerry, Android or Windows phone for a penny in exchange for locking customers into two-year agreements.
A refurbished and "cosmetic blemished" iPhone 3GS can also be had for a penny in this deal. AT&T recently reduced the price of a new iPhone 3GS to $50 with a contract.
One reason for the sale may be AT&T's need to clear inventory to make room for new smartphones using its faster data network. HTC's Inspire 4G goes on sale on Sunday, the same day AT&T begins taking pre-orders for Motorola Mobility's Atrix 4G.
But AT&T, which was the exclusive carrier of the iPhone until last week, is also hoping to mitigate defections now that the largest U.S. carrier by subscribers has cut a deal with Apple. AT&T fired off a marketing blitz last week boasting about iPhone features exclusive to its network.
T-Mobile USA, along with Sprint Nextel, might be more at risk for customers leaving for a highly desirable product (an iPhone) now hitched to a network (Verizon) that's perceived to be very reliable, analysts say.
On Friday and Saturday, T-Mobile stores will offer every phone, smart or not, for free as long as customers sign a two-year contract. The fourth-largest U.S. carrier is painting this as a Valentine's Day promotion, but it's likely that Steve Jobs had more to do with it than Cupid.
T-Mobile also plans to release the Galaxy S 4G from Samsung Electronics this month.
Sprint hasn't gotten aggressive with recent pricing in light of the Verizon iPhone. On the contrary, the third-largest U.S. carrier is moving ahead on an initiative that would increase the monthly price of smartphone customer plans by $10.
On Monday, Sprint unveiled its new Android dual-screen phone, called the Echo from Kyocera.
Even Verizon is looking to capitalize on a hot week for cell phones. As iPhone seekers flocked to its stores, Verizon started taking pre-orders on Thursday for the Pre 2 from Hewlett-Packard. Savvy shoppers would be advised to wait, though. On Wednesday, HP announced that the Pre 3 would be available this summer.