I'll occasionally update this post today and keep the comments section open for discussion of deadline deals.

Minnesota Twins have acquired:
Drew Butera
Low upside/low chance of making the majors. The 23-year-old catcher is patient at the plate but hasn't hit much with a wood bat. He has a strong arm and profiles as a defensive backup catcher at best in the major leagues.
Dustin Martin
Speedy centerfielder has posted nice-looking batting averages and on-base percentages over the past year, but that is unlikely to continue in the upper minor leagues due to strong groundball tendencies (see this article for more information about this).

Cincinnati Reds acquire:
Matt Maloney
The 23-year-old left-handed pitcher was dominant last year and has handled the jump to more age-approrpiate competition at Double-A this year. Maloney has maintained a healthy strikeout rate but occasional control problems and flyball tendencies don't bode well for his future at the hitter-friendly park in Cincinnati. His upside isn't high, but a durable left-handed pitcher at this level has a reasonable chance of seeing some time in a major league bullpen next year.

-- 1:00pm ET Update --

Texas Rangers acquire:

Jarrod Saltalamacchia
Not a minor leaguer, but still a prospect. I've always been positive about Saltalamacchia's bat, even when he was hitting .198 last year. He's a switch-hitter who hit the ball hard - his line drive rates have been above league averages at every level. He has also demonstrated exceptional plate patience at times, so he could be among baseball's on-base leaders if he's still playing in Texas in the prime of his career. His defense gets mixed reports in general, but nearly everyone seems to agree he has made much progress over the past two years.

Neftali Feliz
Feliz is a high-upside pitcher with an oustanding fastball. He will need to stay healthy and greatly improve his control over the next few years to maintain his status as a top prospect, and that's no small order for a 19-year-old who walks a batter every other inning.

Elvis Andrus
I recently wrote: "His performance isn't encouraging, but Andrus is still far too young to write off"

Matt Harrison
Southpaw relies on plus changeup and sinking fastball for strong groundball tendencies that should play well in Texas. His control has been above-average throughout his career.

-- 3:30pm ET Update --

Kansas City Royals acquire:
Kyle Davies
I expect Davies to join the Royals very soon, but he was a minor leaguer this morning so I'll include him in this list. His intriguing stuff simply hasn't played well in the major leagues. The 23-year-old pitcher's control has been poor, and when he's throwing strikes he's been too hittable. Still, you could have said the same thing about Gil Meche six months ago.

Texas Rangers acquire:

Dave Murphy
The former first-round pick's power has never developed as expected, but Murphy is a strong fielder and his plate approach is solid. He could be a solid fourth outfielder for the Rangers as soon as this year.

Engel Beltre
In addition to Gabbard and Murphy, the Rangers are taking a chance on a high-upside guy in the Gagne deal. The Red Sox signed Beltre for $600,000 last summer, when he was among the most highly-touted international free agents. Since then, Beltre's early results in the Gulf Coast League have been typical for a prospect of his nature; he's striking out a lot but also hitting the ball hard when he does make contact.

Chicago White Sox acquire:

Jon Link
Link has struck out over one quarter of opposing batters in the California League, but he's done so as a reliever with the benefit of one of the more pitcher-friendly parks in the California League.

Atlanta Braves acquire:

Royce RIng
Ring has done nothing but dominate Triple-A hitters during the past two years. He struggled with control in a few outings with San Diego this year, but he can miss bats and has exceptional groundball tendencies.

San Diego Padres acquire:
Will Startup
Startup is a Triple-A left-handed reliever with comparable success to Ring, but he's much younger and his flyball tendencies will hurt him less in PETCO.

Seattle Mariners acquire:
Jesus Merchan
Merchan is a utility infielder in his third season of Double-A ball. His greatest skill as a hitter has always been his ability to put the bat on the ball. Until this year that meant a lot of singles and groundouts, but he has hit the ball harder in 2007 and put himself back in consideration as a potential major league role player some day.