What are some events/contests besides GSOC and ICPC that a first year undergrad Computer Science Engineering student should get involved with?
There are lots of international programming competitions for undergraduate students .Here are some of the well known competitions(not mentioned by you).As you didn't mention what kind of competitions you were looking for, here are some general competitions. I have provided links to past problems so you can decide which fits you best.
1.Google Code Jam
Code Jam is Google's longest running global coding competition, where programmers of all levels put their skills to the test. Competitors work their way through a series of online algorithmic puzzles to earn a spot at the World Finals, all for a chance to win the championship title and $15,000.
How it works?
Register and compete in Code Jam’s Online Qualification Round. It lasts 27 hours, but you won't need that long to earn the round’s qualifying point minimum. Once you do, you’ll advance to Online Round 1. They offer three sub-rounds for Round 1, and you can compete in as many as it takes for you to finish in the top 1,500 of any of these rounds.
The top 1,500 from each sub-round move on to compete for a spot in the top 1,000 contestants of Code Jam Online Round 2. These top 1,000 contestants advance to Online Round 3 and earn a limited edition Code Jam t-shirt.
The top 25 contestants from Code Jam Online Round 3 will compete in the Virtual World Finals for the championship title and a cash prize of $15,000.
Past Problems
2.Google Hash Code
Hash Code is a team programming competition, organized by Google, for students and professionals around the world. You pick your team and programming language and we pick an engineering problem for you to solve. This year’s contest kicks off with an Online Qualification, where your team can compete virtually from wherever you’d like, alongside your virtual Hub. Top teams will then be invited to compete from our virtual World Finals.
How it works?
Once you’ve registered for the contest, you’ll gain access to their Judge System. The Judge System is their online platform where you’ll form your team, join a Hub, practice, and compete during the rounds. During the Online Qualification, you’ll watch their YouTube livestream to be introduced to the problem, and your team will have four hours to solve an optimization problem using the programming language and tools of your choice. Teams can also compete alongside other teams in your area by joining a virtual Hub . The top teams from the Online Qualification will be invited to the virtual World Finals, where they’ll work together to solve another challenge and compete for cash prizes.
Past Problems
3.Google Kickstart
Kick Start is a global online coding competition, consisting of three-hour rounds of a variety of algorithmic challenges designed by Google engineers. Participants can compete in one or all online rounds held throughout the year, and will have the opportunity to develop and grow their programming abilities while getting a glimpse into the technical skills needed for a career at Google (top participants may be invited to interview at Google).
How it works
Register for Kick Start once on the website and you’ll be set up to compete in any round you’d like! When each round is open, the three-hour countdown begins and you’ll compete on our website solving algorithmic and mathematical problems. Following the round, you can check out your rankings and the round analysis. If you were a top competitor, you may be contacted by Google for a chance to interview.
Last year's problems
4.Microsoft Imagine Cup
Reimagine technology solutions in a competition designed to help you make a difference in an online world. With four new competition categories—Earth, Education, Health, and Lifestyle—there’s even more opportunity to share your tech ideas for some of today’s most pressing global challenges. What could you create next?
Transform your ideas into action with a purpose-driven application using Microsoft Azure technology. You could win mentorship from Microsoft experts, the chance to showcase your work on a global stage, and other great prizes.
Get Inspired
5.facebook Hacker Cup
Hacker Cup is Facebook's annual open programming competition. Open to participants around the world, we invite you to apply problem-solving and algorithmic coding skills to advance through each year’s online rounds, win prizes, and have a chance to make it to the global finals and win the grand prize.

Last year qualification round
Here are some other &quot;competitions&quot; and resources for practice:
1.Codeforces
Codeforces is a project joining people interested in and taking part in programming contests. On one hand, Codeforces is a social network dedicated to programming and programming contests. On the other hand, it is a platform where contests are held regularly, the participant's skills are reflected by their rating and the former contests can be used to prepare. Codeforces constantly develops and we plan to improve the platform to give the participants the opportunity to organize their own contests, filling the project with learning content, developing Codeforces as a training and learning platform.
It also provides contests and practice for ICPC.
Codeforces conducts different competitions for different rated coders regularly and you can participate in it depending on your Codeforces rating.
Competition structure
It may also conduct competitions with other companies and sponsors at times.
2.atcoder.jp
AtCoder is a programming contest website based in Japan.
There are three types of official contests in AtCoder:

AtCoder Grand Contest (AGC). This is our best contest. The problems will have high originality and require interesting observations.
AtCoder Regular Contest (ARC). The problems may be a bit typical compared to AGC problems, but still we think most of you can enjoy them and they are good for practice.
AtCoder Beginner Contest (ABC). This is mainly targeted for those who are new to competitive programming. The problems will be easy and educational.

3.SPOJ
SPOJ (Sphere Online Judge) is an online judge system with over 315,000 registered users and over 20,000 problems. Tasks are prepared by its community of problem setters or are taken from previous programming contests. SPOJ allows advanced users to organize contests under their own rules and also includes a forum where programmers can discuss how to solve a particular problem.
4.Project Euler
Project Euler is a series of challenging mathematical/computer programming problems that will require more than just mathematical insights to solve. Although mathematics will help you arrive at elegant and efficient methods, the use of a computer and programming skills will be required to solve most problems.
The motivation for starting Project Euler, and its continuation, is to provide a platform for the inquiring mind to delve into unfamiliar areas and learn new concepts in a fun and recreational context.
The intended audience include students for whom the basic curriculum is not feeding their hunger to learn, adults whose background was not primarily mathematics but had an interest in things mathematical, and professionals who want to keep their problem solving and mathematics on the cutting edge.

P.S: There are a lot of other programming competitions but it all depends on your interests(including hackathons, A.I competitions, obscure code competitions etc.)
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